Autoimmune Hepatitis
Autoimmune hepatitis is a chronic inflammatory liver disease caused by an immune-mediated attack against hepatocytes, characterized by elevated transaminases, hypergammaglobulinemia, circulating autoantibodies, and interface hepatitis on biopsy.
Autoimmune Hepatitis (AIH)
Autoimmune hepatitis (AIH) is an immune-mediated chronic hepatitis of unknown etiology characterised by the presence of circulating autoantibodies, hypergammaglobulinaemia (specifically elevated IgG), and necroinflammatory and fibrotic histological changes in the liver [1][2][3].
The name tells you the condition: "auto" = self, "immune" = immune system, "hepatitis" = liver inflammation → the body's own immune system attacks the hepatocytes.
"Chronic hepatitis of unknown etiology. Occurs in all age groups and both sexes across all ethnic groups — female predominance." [1]
Key conceptual points:
- It is not caused by a virus, alcohol, or drug — it is genuinely "autoimmune," where cytotoxic T-lymphocytes target hepatocyte surface antigens.
- It has a heterogeneous and fluctuating nature, leading to marked variability in clinical presentation [3]. A patient can be completely asymptomatic with incidentally deranged LFTs, or present with fulminant hepatic failure.
- It is a diagnosis partly of exclusion — you must rule out viral hepatitis, drug-induced liver injury (DILI), alcoholic liver disease, Wilson's disease, and other causes before labelling someone with AIH [4].
"Variable clinical manifestation — Fluctuating course — Asymptomatic or insidious — Acute severe flare — Fulminant hepatic failure" [1]
Key Concept
AIH is one of the treatable causes of chronic liver disease. Unlike many other liver diseases, it responds dramatically to immunosuppression (corticosteroids ± azathioprine). Missing the diagnosis means missing a highly treatable condition that, left untreated, progresses to cirrhosis in a significant proportion of patients.
2. Epidemiology
- Prevalence: approximately 4–25 per 100,000 population worldwide [5]. It accounts for roughly 10–20% of chronic hepatitis cases in Western countries, and a smaller but increasingly recognised proportion in Asian populations.
- Incidence: approximately 1–2 per 100,000 per year in Europe; data from Hong Kong are limited, but the condition is well-recognised and constitutes a meaningful portion of non-viral chronic liver disease referrals.
- Female predominance: M:F ratio approximately 1:3.6 overall [3]; for Type 1 AIH specifically, F:M ≈ 4:1, and for Type 2, F:M ≈ 10:1 [5].
- Bimodal age distribution: peak incidence in the 2nd–3rd decade (young women) and another peak in 4th–6th decade (peri/post-menopausal women) [2][3].
- However, AIH can occur at any age and in any sex — do not dismiss the diagnosis in an elderly male.
- "Occurs at any age but often diagnosed in 40–50s" [3].
- In HK, Type 1 AIH accounts for > 95% of cases [3][5].
- The relative burden of AIH in HK is overshadowed by the extremely high prevalence of chronic hepatitis B (CHB), but AIH remains an important differential for patients with unexplained chronic hepatitis, particularly HBsAg-negative, anti-HCV-negative patients with elevated transaminases.
- Autoimmune hepatitis is very difficult to diagnose, sometimes becomes a diagnosis of exclusion. Autoantibodies are not specific, require diagnostic criteria. [4]
- HCC is rare in autoimmune hepatitis [7] — this is a notable distinction from HBV/HCV-related cirrhosis where HCC surveillance is paramount. (Note: HCC can still occur in AIH-related cirrhosis, but at much lower rates.)
- AIH occurs across all ethnic groups [1], but the predominant HLA associations and clinical phenotype may vary.
- In Asian populations, Type 1 AIH predominates overwhelmingly.
3. Anatomy and Function: The Liver in Context
To understand AIH, you need to appreciate normal hepatic architecture and why the immune system targets it.
- Hepatocytes are the main parenchymal cells of the liver. They perform synthetic functions (albumin, clotting factors, bile acids), metabolic functions (drug metabolism, bilirubin conjugation), and detoxification.
- Hepatocytes are arranged in lobules around a central vein. At the periphery of each lobule is the portal triad (hepatic artery, portal vein, bile duct).
- The portal tract is the site of maximum inflammation in AIH. Inflammatory infiltrate (lymphocytes, plasma cells) starts at the portal tract and extends into the lobular parenchyma — this is called interface hepatitis (formerly "piecemeal necrosis").
- Kupffer cells (resident macrophages in the liver sinusoids) and dendritic cells present hepatocyte-derived antigens to T-cells, initiating the autoimmune cascade.
- Hepatocyte surface antigens (e.g., the asialoglycoprotein receptor, cytochrome P450 2D6 — the target of anti-LKM1) are the molecular targets of the autoimmune attack.
- The liver is continuously exposed to foreign antigens from the gut via the portal circulation (bacterial products, food antigens). Under normal circumstances, the liver maintains immune tolerance — it preferentially induces tolerance rather than immunity to prevent inappropriate inflammatory responses.
- In AIH, this tolerance breaks down. A combination of genetic susceptibility (HLA) and environmental triggers leads to loss of tolerance to hepatocyte self-antigens.
4. Etiology and Risk Factors
The strongest known risk factors are HLA (Human Leukocyte Antigen) associations:
| AIH Type | HLA Association | Clinical Implication |
|---|---|---|
| Type 1 | HLA-DR3 (DRB1*0301) | Associated with younger age at presentation, decreased response to treatment, more frequent liver failure requiring transplant [3] |
| Type 1 | HLA-DR4 (DRB1*0401) | Generally later onset, better treatment response [3] |
| Type 1 | HLA-DRB3*0101 | Additional susceptibility allele [5] |
| Type 2 | HLA-B14 | Associated with paediatric presentation [3] |
Why HLA matters: HLA molecules on antigen-presenting cells (APCs) present peptide fragments of hepatocyte self-antigens to CD4+ T-helper cells. Certain HLA alleles have a molecular groove that is particularly good at binding and presenting liver-specific autoantigens, thereby triggering an autoimmune T-cell response. This is the same principle as in other HLA-associated autoimmune diseases (e.g., HLA-B27 in ankylosing spondylitis).
The prevailing model is molecular mimicry — an environmental agent (virus, drug, herbal compound) shares structural similarity with a hepatocyte self-antigen. The immune response initially directed against the environmental agent cross-reacts with the self-antigen:
- Viruses: HAV, EBV are most commonly implicated [5]. HCV and measles virus have also been proposed.
- Drugs: Nitrofurantoin, minocycline, methyldopa, hydralazine, statins, anti-TNF agents, checkpoint inhibitors (increasingly important in the modern era of immunotherapy).
- Herbs / Traditional Chinese Medicines (TCMs): Particularly relevant in the Hong Kong context — herbal preparations can trigger both DILI and AIH-like syndromes.
- Immunization: Rarely implicated.
- Regulatory T-cell (Treg) dysfunction: Patients with AIH have reduced numbers and/or function of CD4+CD25+ Tregs, which normally suppress autoreactive T-cells.
- Cytokine milieu: Th1 and Th17-dominant responses drive hepatocyte destruction.
- B-cell activation: Polyclonal B-cell activation leads to the characteristic hypergammaglobulinaemia (elevated IgG) and production of multiple autoantibodies.
Why is IgG specifically elevated?
In AIH, the immune response is predominantly a Th1/Th17-driven adaptive immune response with polyclonal B-cell activation. IgG is the predominant immunoglobulin class produced in chronic immune responses (as opposed to IgM in acute/primary responses). This is why total IgG is elevated (usually with normal IgM and IgA) [2]. This contrasts with PBC, where IgM is characteristically elevated (reflecting a different immunological mechanism).
AIH is commonly associated with other autoimmune diseases, reflecting a general predisposition to immune dysregulation:
| Associated Condition | Approximate Frequency |
|---|---|
| Autoimmune thyroiditis (Hashimoto's) | 8–23% [5] |
| Graves' disease | Part of thyroid spectrum [2] |
| Type 1 diabetes mellitus (T1DM) | 1–10% [5] |
| Ulcerative colitis (UC) | 2–8% [5] |
| Sjögren's syndrome | 1–7% [5] |
| Coeliac disease | 1–6% [5] |
| Rheumatoid arthritis (RA) | 2–4% [5] |
| SLE | 1–2.6% [5] |
| Psoriasis | ~3% [5] |
| Vitiligo | 1–2% [5] |
| Immune thrombocytopenia (ITP) | Recognised association [3] |
"S/S of other autoimmune diseases, e.g. Graves', Hashimoto's thyroiditis, T1DM, UC, RA/SLE" [2]
5. Pathophysiology
Understanding the pathophysiology of AIH requires connecting genetic predisposition → loss of tolerance → immune-mediated hepatocyte destruction → clinical and laboratory manifestations.
Key points:
- CD4+ T-helper cells are the orchestrators — they recognise hepatocyte self-antigens presented on HLA-II molecules by APCs (Kupffer cells, dendritic cells).
- CD8+ cytotoxic T-cells are the executioners — they directly kill hepatocytes expressing the target antigen.
- Autoantibodies (ANA, ASMA, anti-LKM1) are markers of the disease but are not necessarily the direct cause of hepatocyte damage. The damage is primarily T-cell-mediated. However, antibody-dependent cell-mediated cytotoxicity (ADCC) via NK cells may contribute.
- Plasma cell-rich infiltrate at the portal-periportal interface is a histological hallmark.
- Progressive inflammation → bridging necrosis → fibrosis → cirrhosis if untreated.
| Pathological Process | Clinical/Lab Consequence |
|---|---|
| Hepatocyte necrosis | ↑ ALT, ↑ AST (transaminases in hundreds to thousands) |
| Impaired hepatocyte synthetic function | ↓ Albumin, prolonged PT/INR |
| Impaired bilirubin conjugation/excretion | Jaundice (conjugated hyperbilirubinaemia predominantly) |
| Polyclonal B-cell activation | ↑ IgG, presence of autoantibodies |
| Portal/periportal inflammation | Interface hepatitis on biopsy |
| Progressive fibrosis | Cirrhosis → portal hypertension → ascites, varices, splenomegaly |
| Cholestasis (in overlap syndromes) | ↑ ALP, ↑ GGT, pruritus |
6. Classification
"anti-smooth muscle/anti-F actin → type 1; anti-liver kidney microsomal-1 → type 2; anti-liver soluble antigen → type 3; (by experience → type 4)" [1]
| Feature | Type 1 | Type 2 | Type 3 |
|---|---|---|---|
| Characteristic Autoantibodies | ANA, ASMA (anti-smooth muscle Ab), anti-actin Ab (AAA), anti-ssDNA, anti-dsDNA, atypical pANCA | Anti-LKM1 (anti-liver kidney microsomal-1), Anti-LC1 (anti-liver cytosol-1) | Anti-SLA/LP (anti-soluble liver antigen / anti-liver-pancreas antigen) |
| Prevalence | Most common (> 95% in HK / ~80% overall) [3] | Less common | Uncommon; overlaps with Type 1 |
| Age group | Any age; peak 16–30 years, female predominance | Majority children aged 2–14 years | Adults |
| Immunoglobulin elevation | IgG predominance; typically elevated EXCEPT IgA which may be reduced [3] | IgG elevated | IgG elevated |
| Steroid response | Very responsive | Less responsive | Variable |
| Progression to cirrhosis | Less common (~45%) | More common (~82%) | ~75% [5] |
| Other features | Most common worldwide and in HK | More severe, often presents acutely | anti-SLA is the most specific antibody for AIH overall; usually a/w aggressive disease and may lack other autoantibodies [5] |
Some patients have features of both AIH and another autoimmune liver disease:
- AIH–PBC overlap: Features of both AIH (interface hepatitis, elevated IgG, ANA/ASMA) and PBC (elevated ALP/GGT, anti-mitochondrial antibody [AMA] positive, bile duct destruction on biopsy). Treat with UDCA + immunosuppression.
- AIH–PSC overlap: Features of both AIH and PSC (cholangiographic abnormalities). Particularly important in children/young adults with IBD.
AMA (anti-mitochondrial antibody) can rarely be positive in Type 1 AIH without features of PBC [3] — this does not automatically mean overlap syndrome. Clinical, biochemical, and histological correlation is required.
7. Clinical Features
| Symptom | Frequency | Pathophysiological Basis |
|---|---|---|
| Fatigue / Malaise / Lethargy | Very common | Systemic cytokine release (TNF-α, IL-1, IL-6) from chronic inflammation — these cytokines act on the hypothalamus and affect energy metabolism. Also may relate to adrenal axis effects of chronic illness. |
| Anorexia / Nausea | Common | Hepatic inflammation → portal/periportal oedema → impaired bile flow → gastric dysmotility; also cytokine-mediated effects on appetite centres in the hypothalamus |
| Jaundice | Variable; usually mild-moderate [5] | Hepatocyte destruction → impaired bilirubin uptake, conjugation, and excretion; predominantly conjugated (direct) hyperbilirubinaemia because damaged but still-functioning hepatocytes conjugate bilirubin but cannot excrete it efficiently into bile canaliculi |
| Abdominal pain / RUQ discomfort | Common | Hepatic inflammation → swelling of liver parenchyma → distension of the Glisson's capsule (the fibrous capsule surrounding the liver), which is innervated by somatic nerve fibres. The liver parenchyma itself has no pain fibres — so hepatitis causes a dull ache from capsular stretch, not sharp pain [6]. |
| Arthralgia | Characteristic | Arthralgia involving small joints is a characteristic clinical feature though non-specific [3]. Immune complex deposition in synovial membranes and/or circulating cytokines cause joint inflammation. Typically non-erosive (unlike RA). |
| Pruritus | Less common than in PBC/PSC | Cholestasis (impaired bile excretion) → accumulation of bile salts and pruritogens (e.g., lysophosphatidic acid) in the skin. More prominent in overlap syndromes with PBC/PSC. |
| Fever | Intermittent | Systemic inflammatory response; hepatocyte necrosis releasing pyrogens; also IL-1 and IL-6 act on the thermoregulatory centre in the hypothalamus |
| Amenorrhoea | Common in young women | Chronic liver disease impairs hepatic metabolism of oestrogen → hyperestrogenism → hypothalamic-pituitary-gonadal axis suppression. Also, chronic illness itself can suppress GnRH pulsatility. |
| Non-specific erythematous maculopapular rash | Occasional | Immune complex deposition in dermal vessels; vasculitis-like mechanism |
| Myalgia | Occasional | Systemic inflammation; circulating cytokines |
| Sign | Pathophysiological Basis |
|---|---|
| Jaundice (scleral icterus) | As above — bilirubin deposition in tissues with high elastin content (sclera has high affinity for bilirubin) |
| Hepatomegaly | Hepatic inflammation → oedema and swelling of the parenchyma. Liver may be tender on palpation due to capsular distension. |
| Splenomegaly | If cirrhosis develops → portal hypertension → passive congestion of the spleen. Also, reactive lymphoid hyperplasia due to chronic immune activation. |
| Signs of chronic liver disease | Spider naevi (oestrogen-mediated arteriolar dilatation in SVC distribution), palmar erythema (hyperdynamic circulation + oestrogen), gynaecomastia (impaired oestrogen metabolism), caput medusae, ascites, peripheral oedema — all indicating cirrhosis ± portal hypertension |
| Cushingoid features | May be present if patient has been on long-term corticosteroid therapy (iatrogenic) |
| Acne / Striae | As above — steroid side effects |
| Signs of associated autoimmune diseases | Goitre (thyroiditis/Graves'), dry eyes/mouth (Sjögren's), joint deformities (RA), malar rash (SLE), skin depigmentation (vitiligo) |
| Excoriations / scratch marks | If pruritus is present (more so in overlap syndromes) |
7.4 Presentation Patterns in Detail
"Chronic hepatitis (majority) — Asymptomatic: present with incidental finding of ↑transaminases or cryptogenic cirrhosis in elderly (d/dx: NASH)" [5]
- Most common presentation. Patients may be completely asymptomatic — found to have elevated ALT/AST on routine blood tests (e.g., health check, insurance medical, pre-operative workup).
- Others have an insidious onset over weeks to months of fatigue, anorexia, nausea, vague abdominal discomfort, arthralgia.
- Jaundice is usually mild to moderate.
- Some present with cryptogenic cirrhosis — by the time they are diagnosed, the "burnt-out" phase has established cirrhosis. The autoantibodies may even be negative at this stage, making diagnosis challenging. This is particularly seen in elderly patients.
"Acute liver failure (25%)" [2] "Transaminases in thousands but negative for ALL viral hepatitis markers" [5]
- Mimics acute viral hepatitis clinically and biochemically — the patient has jaundice, malaise, nausea, and transaminases in the thousands.
- Key clue: all viral markers are negative (HBsAg−, anti-HCV−, IgM anti-HAV−, IgM anti-HEV−).
- Does not resolve completely after 6 months [5] — this is the key temporal distinction from a self-limiting acute viral hepatitis.
- Can progress to acute liver failure (ALF) / fulminant hepatic failure, with coagulopathy (INR > 1.5) and encephalopathy.
- A small but important subset presents with fulminant liver failure.
- These patients may lack classical autoantibodies at presentation (antibodies may be "consumed" or not yet detectable), making diagnosis extremely challenging.
- The autoantibody profile may initially be negative in fulminant presentations — consider AIH in any patient with unexplained fulminant liver failure after excluding paracetamol, viral, Wilson's, and other causes.
Clinical Pearl: AIH Mimicking Acute Viral Hepatitis
A common exam pitfall is a young woman presenting with what looks like acute viral hepatitis (transaminases > 1000, jaundice) — but all viral serology comes back negative. The trap is to dismiss the case and not consider AIH. Always check IgG levels and autoantibodies (ANA, ASMA, anti-LKM1) in any case of acute hepatitis with negative viral markers. This is a classic OSCE/MCQ scenario.
While formal investigations will be discussed later, certain laboratory patterns are so characteristic that they are considered part of the clinical presentation:
- Hepatitic LFT pattern: ↑ ALT, ↑ AST [2] — typically ALT > AST (as in most primary liver diseases [8]).
- In most primary liver pathologies, ALT rises more than AST. In AIH, this pattern holds unless cirrhosis has developed (in cirrhosis, the AST:ALT ratio reverses because AST is released from mitochondria of damaged cells in a cirrhotic liver with reduced ALT clearance).
- Transaminases can range from mildly elevated (< 5× ULN in smouldering disease) to markedly elevated (> 10–50× ULN in acute flares).
- ↑ Total IgG (usually normal IgM, IgA) [2] — a key distinguishing feature. The IgG elevation is usually polyclonal on serum protein electrophoresis (broad-based gamma band, not a monoclonal spike).
- Positive autoantibodies: ANA, ASMA, anti-LKM1, anti-SLA/LP — these are discussed in classification above.
- Normal or only mildly elevated ALP and GGT — this distinguishes AIH from cholestatic diseases (PBC, PSC). If ALP is disproportionately elevated, think overlap syndrome.
| Feature | AIH | PBC | PSC |
|---|---|---|---|
| Primary target | Hepatocytes | Small intrahepatic bile ducts | Large intra/extrahepatic bile ducts |
| Demographics | Young/middle-aged women | Middle-aged women (90–95% female) | Young men (M > F, 2:1) |
| Key autoantibody | ANA, ASMA (Type 1); anti-LKM1 (Type 2) | AMA (M2 isoform — highly specific) [7] | pANCA (non-specific) |
| Predominant Ig | IgG | IgM | — |
| LFT pattern | Hepatitic (↑ALT/AST) | Cholestatic (↑ALP/GGT) | Cholestatic (↑ALP/GGT) |
| Associated disease | Multiple autoimmune conditions | Sjögren's, scleroderma, Hashimoto's | Strong association with UC [9] |
| Treatment | Steroids ± azathioprine | UDCA ± obeticholic acid | UDCA (limited benefit); transplant |
| HCC risk | Rare [7] | Low but present with cirrhosis | Higher (also cholangiocarcinoma risk) |
8. Important Associations and Context
- Some drugs can trigger a true AIH (not just DILI) — the distinction is that drug-induced AIH persists even after drug withdrawal and requires immunosuppressive treatment.
- Key drugs: nitrofurantoin, minocycline, infliximab, checkpoint inhibitors (nivolumab, pembrolizumab — increasingly important).
- In the HK context, herbal medications and TCMs are an important trigger to consider.
- AIH can recur after liver transplantation (occurs in ~20–40% of cases).
- De novo AIH can also develop post-transplant in patients who did not originally have AIH.
- AIH may flare postpartum — the relative immunosuppression of pregnancy often leads to disease quiescence, followed by a flare in the postpartum period as the immune system "rebounds."
- Azathioprine is considered relatively safe in pregnancy (Category D, but extensive clinical experience supports continuation).
High Yield Summary
Definition: Immune-mediated chronic hepatitis of unknown aetiology, characterised by autoantibodies, ↑IgG, and interface hepatitis on biopsy.
Epidemiology: Female predominance (F:M ≈ 4:1); bimodal age distribution (young adults and peri-menopausal); Type 1 accounts for > 95% of cases in HK.
Pathophysiology: Genetic susceptibility (HLA-DR3/DR4) + environmental trigger → loss of immune tolerance to hepatocyte antigens → CD4/CD8 T-cell-mediated hepatocyte destruction + polyclonal B-cell activation (↑IgG, autoantibodies).
Classification: Type 1 (ANA/ASMA), Type 2 (anti-LKM1), Type 3 (anti-SLA/LP — most specific).
Clinical Features:
- Variable: asymptomatic → chronic hepatitis → acute hepatitis → fulminant liver failure.
- Key symptoms: fatigue, jaundice, arthralgia (small joints), abdominal discomfort, anorexia.
- Key signs: hepatomegaly, jaundice, signs of chronic liver disease if cirrhosis present, signs of associated autoimmune diseases.
- Lab hallmarks: ↑ALT/AST (hepatitic pattern), ↑IgG (normal IgM/IgA), positive autoantibodies.
HCC risk is rare in AIH (unlike HBV/HCV cirrhosis).
Diagnosis is partly by exclusion — must rule out viral hepatitis, DILI, alcohol, Wilson's, metabolic causes.
Key exam scenarios: Young woman with acute hepatitis and negative viral markers; cryptogenic cirrhosis in an elderly patient; patient with multiple autoimmune diseases found to have elevated transaminases.
Active Recall - Autoimmune Hepatitis (Definition to Clinical Features)
[1] Lecture slides: Teaching Clinic - Non-viral chronic liver diseases (Prof. Yuen Man Fung) 2.pdf [2] Senior notes: Maksim Medicine Notes.pdf (p.150, Autoimmune hepatitis section) [3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.730–731, Autoimmune hepatitis) [4] Senior notes: Block A - Gastrointestinal Data Interpretation.pdf (p.2) [5] Senior notes: Ryan Ho GI.pdf (p.280, section 4.4.1 Autoimmune Hepatitis) [6] Senior notes: Block A - Jaundice after raw oysters_ acute hepatitis.pdf (p.2) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.2) [8] Senior notes: Block A - Introduction to GI_Hepatology investigations (LFT, Endoscopy).pdf (p.5) [9] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p.531, PSC section)
Differential Diagnosis of Autoimmune Hepatitis
The differential diagnosis of AIH is arguably more important than its positive diagnosis, because autoimmune hepatitis is very difficult to diagnose, sometimes becomes a diagnosis of exclusion [4]. The autoantibodies are not pathognomonic — they can be found in other liver diseases and even in healthy individuals at low titres. Therefore, you must systematically exclude mimics before confidently diagnosing AIH.
The differential depends entirely on how the patient presents. AIH is a chameleon — it can mimic acute viral hepatitis, chronic hepatitis, cholestatic liver disease, or cryptogenic cirrhosis. Let's organise the differential by clinical scenario.
Differential diagnosis of AIH: Acute hepatitis, Chronic hepatitis, Primary biliary cholangitis, Primary sclerosing cholangitis, Wilson's disease, Hepatic haemochromatosis [3]
2. Differential Diagnosis: Acute Hepatitis Presentation
When AIH presents acutely (transaminases in the thousands, jaundice), it mimics acute viral hepatitis. The key differentials are:
| Feature | Viral Hepatitis | AIH |
|---|---|---|
| Viral markers | Positive (IgM anti-HAV, HBsAg/IgM anti-HBc, IgM anti-HEV, anti-HCV) | Negative for ALL viral hepatitis markers [5] |
| Epidemiological clue | Travel, raw seafood (HAV/HEV); blood-borne risk factors (HBV/HCV) | No viral exposure history |
| Self-resolution | Usually resolves within 6 months (except HCV) | Does not resolve completely after 6 months [5] |
| IgG level | Normal or mildly elevated | Elevated total IgG |
| Autoantibodies | Negative or low-titre | Positive ANA/ASMA/anti-LKM1 |
Why this matters in HK: Hong Kong has a very high prevalence of chronic HBV (~7–8% carrier rate). Any patient presenting with acute hepatitis must have HBV serology checked. Anti-HBc IgM can be positive in both acute HBV infection AND acute flare of chronic HBV infection [4] — so a positive IgM anti-HBc does not automatically mean acute infection. You need the clinical context.
HAV and HEV are faeco-orally transmitted. In HK, half of us will have positive IgG for Hep A — such a common virus [4]. So IgG anti-HAV is not helpful — only IgM anti-HAV diagnoses acute HAV infection.
High Yield Exam Point
The classic exam scenario: a young woman presents with acute hepatitis (ALT > 1000, jaundice). All viral markers are negative. The reflex next step is to check serum IgG and autoantibodies (ANA, ASMA, anti-LKM1). If IgG is elevated and autoantibodies are positive, AIH is the leading diagnosis.
| Feature | DILI | AIH |
|---|---|---|
| Drug history | Temporal relationship with offending drug | No culprit drug identified |
| Pattern | Can present all forms of liver injury — hepatitic, cholestatic, mixed pattern, cirrhosis [2] | Predominantly hepatitic |
| Course after withdrawal | Improves after drug withdrawal | Persists or relapses after drug withdrawal |
| Autoantibodies | Can be positive (especially with nitrofurantoin, minocycline) | Positive |
| IgG | Usually normal | Elevated |
| Rechallenge | Recurs if drug re-introduced | N/A |
Why this is tricky: Some drugs (nitrofurantoin, minocycline, methyldopa, statins, anti-TNF agents, checkpoint inhibitors, herbal medications) can cause a drug-induced autoimmune hepatitis that is serologically indistinguishable from idiopathic AIH. The key differentiator is:
- Drug-induced AIH resolves after drug withdrawal and does not require long-term immunosuppression.
- True AIH triggered by a drug persists after withdrawal and requires ongoing treatment.
In the HK context, always ask about TCM/herbal supplement use — this is a frequently tested point.
| Feature | Alcoholic Hepatitis | AIH |
|---|---|---|
| History | Significant alcohol intake | Usually non-drinker or social drinker |
| AST:ALT ratio | AST > ALT, > 2:1 ratio [8] | ALT > AST (unless cirrhosis) |
| AST level | Serum AST almost never > 500 U/L [8] | Can be > 1000 U/L in acute flares |
| GGT | Isolated rise in GGT with relatively normal ALP (GGT is inducible by alcohol) [10] | Usually not prominently elevated |
| MCV | Increased MCV — toxic alcohol permeates RBC membrane and alters lipid structures [8] | Normal MCV |
| Immunoglobulin | ↑ IgA = Alcoholic hepatitis [3] | ↑ IgG = Autoimmune hepatitis [3] |
| Parotid enlargement | Present | Absent |
Immunoglobulin pattern in different liver diseases: ↑ IgG = Autoimmune hepatitis; ↑ IgM = Primary biliary cholangitis (PBC); ↑ IgA = Alcoholic hepatitis [3]
This is a must-know pattern for exams.
| Feature | Ischaemic Hepatitis | AIH |
|---|---|---|
| Clinical context | Profound shock, haemodynamic instability [8] | No haemodynamic compromise |
| AST:ALT | AST > ALT [8] | ALT > AST |
| LDH | Disproportionate increase in LDH [8] | Normal or mildly elevated LDH |
| Course | Rapid fall of near 1000 units a day — characteristic rapid decline once perfusion restored [8][10] | Does not show such rapid decline |
| ALT/AST trajectory | Levels fall dramatically within 1–3 days | Gradual improvement with treatment |
Ischaemic hepatitis is one of three conditions causing a rapid decline in ALT/AST: (1) acute ischaemic hepatitis, (2) paracetamol overdose, (3) cholangiohepatitis [8].
Wilson's disease ("wilso" = pertaining to S.A.K. Wilson who described it; "hepatolenticular degeneration" = liver + lentiform nucleus damage) is a critical differential, especially in young patients (age 5–35) [11].
| Feature | Wilson's Disease | AIH |
|---|---|---|
| Age | Usually 5–35 years (average 13) [11] | Any age, peak 16–30 and 40–50 |
| Ceruloplasmin | Low (< 20 mg/dL) | Normal |
| 24h urinary copper | Elevated | Normal |
| Kayser-Fleischer rings | Present on slit-lamp examination | Absent |
| Neuropsychiatric features | Can mimic Parkinson's — extrapyramidal deposition of copper [7] | Absent |
| Fulminant presentation | Young patients with no reason for fulminant liver failure — only finding is low haemoglobin — Coombs-negative haemolytic anaemia [7] | No haemolysis |
| Histology | Similar to AIH and NASH — fatty infiltration, glycogen inclusions, portal fibrosis [12] | Interface hepatitis with plasma cells |
| Genetic testing | Does not have to be positive to reach diagnosis — hereditary pathway is heterogeneous, not just ATP7B [7] | N/A |
Wilson's vs AIH in Fulminant Liver Failure
Fulminant hepatic failure due to Wilson's has a very specific feature: young patients with no reason for fulminant liver failure, exclusion of all other common causes → only finding is low haemoglobin. Coombs-negative haemolytic anaemia [7]. This is because massive copper release from necrotic hepatocytes causes oxidative damage to RBC membranes, leading to non-immune haemolysis. AIH-related fulminant liver failure does NOT cause Coombs-negative haemolytic anaemia.
3. Differential Diagnosis: Chronic Hepatitis Presentation
When AIH presents as persistent elevation of transaminases (the most common scenario, often asymptomatic), the differential is broader:
- In HK, chronic HBV is by far the most common cause of persistently elevated transaminases [4][13].
- HCV is less common in HK but still must be excluded — anti-HCV is the screening test; it's hard to catch the acute phase unless you have had a needlestick injury [4].
- Dual liver disease is common in HK [13] — a patient can have both HBV and AIH, or HBV and MASLD simultaneously. Always think about co-existent pathology.
| Feature | MASLD | AIH |
|---|---|---|
| Risk factors | Obesity, DM, metabolic syndrome | Autoimmune predisposition, female |
| LFT elevation | Usually mild (< 5× ULN); ALT > AST | Can be any degree; ALT > AST |
| Imaging | Steatosis on USG/FibroScan (CAP score > 248 dB/m) [13] | No steatosis unless co-existent |
| Autoantibodies | Can be low-titre positive (ANA up to 1:320 in ~20% of MASLD) | Usually higher titres; ASMA more specific |
| IgG | Normal | Elevated |
| Histology | Steatosis, ballooning, lobular inflammation | Interface hepatitis, plasma cells |
Important caveat: Low-titre ANA can be positive in MASLD, making it a potential confounder. Autoantibodies are not specific, require diagnostic criteria [4].
In elderly patients with cryptogenic cirrhosis, the main differential is between "burnt-out" AIH and MASLD/NASH-related cirrhosis [5]. By the time cirrhosis is established, the original features (steatosis in MASLD; autoantibodies in AIH) may have disappeared, making differentiation very difficult.
| Feature | Haemochromatosis | AIH |
|---|---|---|
| Demographics | Males > females (females protected by menstruation); presents age 40–60 | Females > males; bimodal |
| Iron studies | ↑ Ferritin, ↑ transferrin saturation (> 45%) | Normal iron studies |
| Skin | Bronze discolouration ("bronze diabetes") | No pigmentary changes |
| Other organs | DM, cardiomyopathy, arthropathy, hypogonadism | Extrahepatic autoimmune diseases |
| Genetic testing | HFE gene mutation (C282Y homozygosity) | HLA-DR3/DR4 association |
| Histology | Iron deposition (Prussian blue stain) | Plasma cell-rich interface hepatitis |
- Rare but important, especially in younger patients with unexplained chronic liver disease.
- Diagnosed by low serum α1-antitrypsin level and characteristic PAS-positive, diastase-resistant globules on liver biopsy.
- Think of it when you have chronic hepatitis without viral/autoimmune/metabolic causes.
4. Differential Diagnosis: Cholestatic Presentation
Occasionally, AIH can present with a cholestatic picture (↑ ALP/GGT, pruritus). In this scenario, the main differentials are other autoimmune cholestatic liver diseases:
| Feature | PBC | AIH |
|---|---|---|
| Target | Small intralobular bile ducts [9] | Hepatocytes |
| Demographics | Extreme female predominance (90–95%); age 30–65 [9] | Female predominance; bimodal |
| Key symptom | Pruritus (worse at night) and fatigue [9] | Fatigue, arthralgia, jaundice |
| Key antibody | AMA M2 isoform — highly specific for PBC [7] | ANA, ASMA, anti-LKM1 |
| Immunoglobulin | ↑ IgM | ↑ IgG |
| LFT pattern | Cholestatic (↑ ALP/GGT) | Hepatitic (↑ ALT/AST) |
| Associated diseases | Sjögren's syndrome (40–65%), scleroderma (5–10%), Hashimoto's thyroiditis (10–15%) [9] | Various autoimmune diseases |
| Cholangiography | Normal | Normal |
| Treatment | UDCA [7] | Steroids ± azathioprine |
Overlap syndrome (AIH-PBC): When a patient has features of both (e.g., elevated ALP + AMA positive + elevated ALT + ANA/ASMA positive + interface hepatitis on biopsy), an overlap syndrome should be considered. Treatment typically involves both UDCA and immunosuppression.
| Feature | PSC | AIH |
|---|---|---|
| Target | Large intra/extrahepatic bile ducts [14] | Hepatocytes |
| Demographics | Young men (M > F) | Young/middle-aged women |
| Key association | STRONG association with UC [14] | Multiple autoimmune diseases (UC less prominent) |
| Key antibody | pANCA (non-specific) | ANA, ASMA |
| Cholangiography | Multifocal strictures and dilatation ("beaded" appearance) | Normal |
| Cholangiocarcinoma risk | Significant (10–15% lifetime) | Low |
| Treatment | UDCA (limited benefit); liver transplant | Steroids ± azathioprine |
- A newer entity — part of the IgG4-related disease spectrum.
- Presents with obstructive jaundice and biliary strictures mimicking cholangiocarcinoma or PSC.
- Distinguished by elevated serum IgG4 (> 1.35 g/L) and IgG4-positive plasma cells on biopsy.
- Important to differentiate from PSC and AIH-PSC overlap.
- Responds to corticosteroids (unlike PSC).
When AIH presents as acute liver failure (ALF), the differential includes all causes of ALF:
| Cause | Key Differentiating Feature |
|---|---|
| Paracetamol overdose | Drug history; paracetamol level at 4h; rapid fall in ALT/AST after peak [8] |
| Acute viral hepatitis (HAV/HBV/HEV) | Positive viral serology [15] |
| Wilson's disease (fulminant) | Young patient, Coombs-negative haemolytic anaemia, low ceruloplasmin, high urinary copper [7] |
| Drug/herbal toxicity | Drug history, temporal relationship |
| Pregnancy-related (HELLP/AFLP) | HELLP syndrome: Haemolysis, Elevated Liver enzymes, Low Platelets [15]; 3rd trimester |
| Ischaemic hepatitis | Haemodynamic instability, disproportionate LDH elevation, rapid ALT/AST decline [8] |
| AIH | Elevated IgG, positive autoantibodies (but may be negative in fulminant phase) |
Pitfall in Fulminant AIH
In fulminant AIH, autoantibodies may be negative or low-titre because they are "consumed" in the immune process or overwhelmed by the massive hepatocyte necrosis. The IgG may also not be strikingly elevated if the liver is failing catastrophically. In such cases, a liver biopsy (if safe) showing plasma cell-rich interface hepatitis, or an empirical trial of corticosteroids with close monitoring, may be necessary. This is one reason why AIH can be a diagnosis of exclusion.
| Differential | Key distinguishing test/feature | Why it matters for AIH workup |
|---|---|---|
| Chronic HBV | HBsAg, HBV DNA | Most common chronic hepatitis in HK [4]; must exclude before diagnosing AIH |
| Chronic HCV | Anti-HCV, HCV RNA | Causes chronic hepatitis and cirrhosis |
| MASLD/NASH | BMI, metabolic risk factors, imaging for steatosis, FibroScan CAP score | Can have low-titre ANA; distinguish from AIH by IgG level and histology |
| Alcoholic liver disease | Alcohol history; AST:ALT > 2:1, AST < 500; ↑GGT, ↑MCV, ↑IgA [8] | Must exclude |
| DILI | Drug/herbal history; temporal relationship; improves with withdrawal | Can present all forms of liver injury [2] |
| Wilson's disease | Low ceruloplasmin, 24h urinary copper, KF rings, genetic testing | Histologically similar to AIH [12]; must exclude in patients < 40 |
| Haemochromatosis | Iron studies (ferritin, transferrin saturation), HFE genotyping | Exclude in chronic hepatitis workup |
| α1-antitrypsin deficiency | Serum α1-antitrypsin level | Rare but treatable |
| PBC | AMA (M2 isoform), ↑IgM, cholestatic LFT pattern [7] | Exclude if cholestatic features; consider overlap |
| PSC | Cholangiography (MRCP/ERCP), association with UC [14] | Exclude if cholestatic features; consider overlap |
| IgG4-related cholangitis | Serum IgG4, IgG4+ plasma cells on biopsy | Mimics PSC; responds to steroids |
The systematic workup to exclude differentials before diagnosing AIH follows this logical sequence:
High Yield: The 'Diagnosis by Exclusion' Principle
Diagnosis by exclusion: viral hepatitis, DILI, alcoholic liver disease [2]. In practice, you must systematically exclude viral causes (HBV, HCV, HAV, HEV), drug/herbal causes, alcohol, and metabolic causes (Wilson's, haemochromatosis) before diagnosing AIH. Only after these are excluded AND autoimmune markers are positive do you proceed to biopsy for confirmation.
- HBV prevalence: HBV is endemic in HK. Always check HBsAg and anti-HBc. Importantly, dual liver disease (HBV + AIH, or HBV + MASLD) is common in HK [13]. A patient can be HBsAg-positive AND have AIH — they are not mutually exclusive, though this makes management more complex.
- MASLD/NASH: With rising obesity rates in HK, MASLD is increasingly the most common cause of persistently elevated ALT. 90% of autoimmune hepatitis cases will present asymptomatic — incidental finding [7], which is also the typical MASLD presentation. Distinguish them by IgG level, autoantibody titres, and biopsy.
- Herbal/TCM use: Common in HK. Always take a thorough drug and supplement history.
- HCC is rare in autoimmune hepatitis [7] — this is a distinguishing point from HBV/HCV-related cirrhosis. However, if AIH progresses to cirrhosis, HCC surveillance is still recommended (though less stringently than for HBV cirrhosis).
High Yield Summary: Differential Diagnosis of AIH
-
The differential depends on the presentation — acute hepatitis vs chronic hepatitis vs cholestatic vs fulminant vs cryptogenic cirrhosis.
-
Must-exclude differentials: Viral hepatitis (HBV, HCV, HAV, HEV), DILI (including herbal/TCM), alcoholic liver disease, Wilson's disease, haemochromatosis, α1-antitrypsin deficiency, PBC, PSC.
-
Key differentiating features of AIH: Negative viral markers, no drug/alcohol history, elevated IgG (not IgM or IgA), positive autoantibodies (ANA/ASMA/anti-LKM1/anti-SLA), interface hepatitis with plasma cells on biopsy.
-
Immunoglobulin pattern: ↑IgG = AIH; ↑IgM = PBC; ↑IgA = Alcoholic hepatitis.
-
AST:ALT ratio: ALT > AST in most primary liver diseases including AIH; AST > ALT in alcoholic hepatitis (> 2:1), HCC, CHF, ischaemic hepatitis.
-
Wilson's in fulminant liver failure: Coombs-negative haemolytic anaemia + low ceruloplasmin is the clue.
-
HK context: Always exclude HBV first; dual liver disease is common; ask about TCM/herbal use; MASLD is increasingly prevalent.
Active Recall - Differential Diagnosis of AIH
References
[2] Senior notes: Maksim Medicine Notes.pdf (p.150, Autoimmune hepatitis section) [3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.730–732, Autoimmune hepatitis) [4] Senior notes: Block A - Gastrointestinal Data Interpretation.pdf (p.2) [5] Senior notes: Ryan Ho GI.pdf (p.280, section 4.4.1 Autoimmune Hepatitis) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.1–2) [8] Senior notes: Block A - Introduction to GI_Hepatology investigations (LFT, Endoscopy).pdf (p.5, p.16–17) [9] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p.535, PBC section) [10] Senior notes: Block A - Introduction to GI_Hepatology investigations (LFT, Endoscopy).pdf (p.10) [11] Senior notes: Adrian Lui Pediatrics Notes.pdf (p.266, Wilson Disease) [12] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p.386, Wilson's disease) [13] Senior notes: Block A - Gastroenterology Interactive Tutorial.pdf (p.2) [14] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p.531, PSC section) [15] Senior notes: Block A - A jaundiced and incoherent patient_ liver failure.pdf (p.3)
Diagnostic Criteria, Algorithm, and Investigations for Autoimmune Hepatitis
Before diving into criteria and algorithms, it is essential to understand why AIH is notoriously hard to diagnose:
- Autoimmune hepatitis, very difficult to diagnose, sometimes becomes a diagnosis of exclusion [4].
- Autoantibodies are not specific, require diagnostic criteria [4].
- There is no single pathognomonic test. ANA can be found in healthy individuals, MASLD, and other liver diseases. ASMA can be low-titre positive in various conditions. Even elevated IgG is not unique to AIH.
- The clinical presentation is a chameleon — it can mimic acute viral hepatitis, chronic hepatitis, cholestatic disease, or cryptogenic cirrhosis.
- Therefore, diagnosis relies on a composite scoring system that integrates clinical, serological, biochemical, and histological data, combined with exclusion of other causes.
"Determining the final diagnosis requires: History (drug history), Clinical presentation, Other investigations, Liver biopsy may be required" [16]
2. Diagnostic Criteria
This is the original comprehensive scoring system. It was designed primarily for research purposes but is used clinically for complex or atypical cases. It produces a pre-treatment and post-treatment score.
| Parameter | Score |
|---|---|
| Sex: Female | +2 |
| ALP:AST (or ALT) ratio | |
| — < 1.5 | +2 |
| — 1.5–3.0 | 0 |
| — > 3.0 | −2 |
| Serum globulins or IgG above ULN | |
| — > 2.0× ULN | +3 |
| — 1.5–2.0× ULN | +2 |
| — 1.0–1.5× ULN | +1 |
| — < 1.0× ULN | 0 |
| ANA, ASMA, or anti-LKM1 | |
| — > 1:80 | +3 |
| — 1:80 | +2 |
| — 1:40 | +1 |
| — < 1:40 | 0 |
| AMA positive | −4 |
| Viral markers (IgM anti-HAV, HBsAg, IgM anti-HBc, anti-HCV) | |
| — Positive | −3 |
| — Negative | +3 |
| Drug history | |
| — Positive (hepatotoxic drug) | −4 |
| — Negative | +1 |
| Alcohol intake | |
| — < 25 g/day | +2 |
| — > 60 g/day | −2 |
| Histology | |
| — Interface hepatitis | +3 |
| — Plasma cells predominant | +1 |
| — Rosette formation | +1 |
| — None of the above | −5 |
| — Biliary changes | −3 |
| — Other atypical features | −3 |
| Other autoimmune diseases (in patient or 1st-degree relative) | +2 |
| Additional parameters | |
| — Anti-SLA/LP, anti-actin, anti-LC1, pANCA positive | +2 |
| — HLA-DR3 or DR4 | +1 |
| Response to corticosteroids | |
| — Complete | +2 |
| — Relapse | +3 |
Interpretation:
| Pre-treatment Score | Post-treatment Score | Diagnosis |
|---|---|---|
| > 15 | > 17 | Definite AIH |
| 10–15 | 12–17 | Probable AIH |
Why this scoring system matters: It gives the most comprehensive assessment but is complex for routine use. It incorporates response to treatment — if a patient responds beautifully to steroids, this adds points and supports the diagnosis retrospectively.
This is the practically used, exam-friendly scoring system designed for clinical use — simpler, fewer parameters, validated for routine practice.
| Variable | Cut-off | Points |
|---|---|---|
| ANA or ASMA | ≥ 1:40 | 1 |
| ≥ 1:80 | 2* | |
| or anti-LKM1 | ≥ 1:40 | 2* |
| or anti-SLA/LP | Positive | 2* |
| IgG level | > ULN | 1 |
| > 1.1× ULN | 2 | |
| Liver histology | Compatible with AIH | 1 |
| Typical of AIH | 2 | |
| Absence of viral hepatitis | Yes | 2 |
*Maximum 2 points for autoantibodies (even if multiple are positive)
Interpretation:
| Total Score | Diagnosis |
|---|---|
| ≥ 6 | Probable AIH |
| ≥ 7 | Definite AIH |
High Yield: Simplified Criteria for Exams
For HKUMed exams, the Simplified Criteria are the most likely to be tested. Remember the four pillars: Autoantibodies, IgG level, Histology, Exclusion of viral hepatitis. A score of ≥ 7 = definite AIH, ≥ 6 = probable AIH. The maximum possible score is 8 (2 for autoantibodies + 2 for IgG + 2 for histology + 2 for negative viral markers).
| Histological Feature | Typical AIH | Compatible with AIH | Atypical |
|---|---|---|---|
| Interface hepatitis | Present (marked) | Present (mild) | Absent |
| Lymphoplasmacytic infiltrate in portal tracts extending into lobule | Prominent; plasma cells predominant | Present but less prominent | Absent |
| Emperipolesis (penetration of intact cells by lymphocytes) | Present | May be present | Absent |
| Hepatocyte rosette formation | Present | May be present | Absent |
| Fibrosis | Bridging fibrosis or cirrhotic nodules | Any degree | — |
| Biliary changes (bile duct damage, granulomas) | Absent | Absent | Present → think PBC/PSC overlap |
"Plasma cells infiltrating the liver → specific feature of autoimmune hepatitis" [7]
"Presence of interface hepatitis. Presence of lymphocytic or lymphoplasmacytic infiltrates in the portal tracts and extending into lobules. Fibrosis is present in all forms of autoimmune hepatitis which connects portal and central areas (bridging) and ultimately leads to cirrhosis" [3]
Why "interface hepatitis" matters: Interface hepatitis means the inflammatory infiltrate at the portal-periportal boundary is breaching the limiting plate and invading the hepatic lobule. This is the hallmark lesion. "Interface" = at the interface between the portal tract and the parenchyma. It used to be called "piecemeal necrosis" — the hepatocytes at the edge of the lobule are being picked off one by one by cytotoxic T-cells and plasma cells.
Important Principle: Only Image When There Is a Physical Entity
"Prof really emphasizes this point → only when there is a physical entity causing the pathology, imaging is helpful. In other cases, a diagnosis can be made using solely clinical and laboratory investigations. Don't expose patients to unnecessary radiation, and don't clog up the wait times." [8] For AIH, the diagnosis is made by blood tests + biopsy. Imaging (USG) is used to exclude biliary obstruction and assess for cirrhosis/portal hypertension, NOT to diagnose AIH itself.
4. Investigation Modalities: Detailed Breakdown
4.1 Liver Function Tests (LFT)
The LFT is the starting point. It tells you three things about the liver:
"Liver function tests assess three distinct aspects of hepatic function: cellular integrity through ALT and AST levels, synthetic capacity via albumin and prothrombin time, and excretory function using bilirubin, ALP and GGT" [17]
| Parameter | AIH Findings | Interpretation |
|---|---|---|
| ALT | Elevated (range: mildly elevated to > 1000 in acute flares) | ALT is predominantly cytoplasmic, more liver-specific than AST |
| AST | Elevated, usually ALT > AST | AST has both cytoplasmic and mitochondrial isoforms; in most primary liver diseases, ALT > AST [8] |
| AST:ALT ratio | Usually < 1 (ALT dominant) | If AST > ALT, think: alcoholic hepatitis, HCC, CHF, ischaemic hepatitis [8]. In AIH-related cirrhosis, the ratio may reverse because cirrhotic liver has reduced capacity to clear AST. |
- "Very severe acute insult, AST will increase before ALT — most vulnerable organelles in the cell is mitochondria → so will die first during insult, and are released into blood first" [8]
- "AST has a shorter half-life than ALT → AST falls faster. AST 17 ± 5 hrs, ALT 47 ± 10 hrs. Memory: S in AST indicates shorter, L in ALT is longer" [8]
In AIH specifically:
- Chronic smouldering: ALT mildly elevated (1–5× ULN)
- Acute flare: ALT can be > 10–50× ULN (thousands)
- Occasionally autoimmune hepatitis can give a cholestatic picture marked by high level of conjugated bilirubin and ALP [3] — if this occurs, you must rule out extrahepatic obstruction, PBC, and PSC.
| Parameter | AIH Findings | Interpretation |
|---|---|---|
| Albumin | Normal in early disease; low if cirrhosis or severe acute disease | Albumin is not very sensitive or specific for liver synthetic function because (1) the liver can synthesise at twice the basal rate (compensatory reserve), (2) long half-life (~20 days) means it only drops in chronic or severe disease, (3) other causes of low albumin exist (nephrotic syndrome, sepsis, malnutrition) [8] |
| PT/INR | Normal in early disease; prolonged in severe disease or cirrhosis | PT/INR reflects factor VII (shortest half-life coagulation factor, ~6h) — this makes INR the best real-time marker of synthetic function. If ALT is falling AND INR is improving → patient is recovering. If ALT is falling AND INR is worsening → fulminant hepatitis (the liver is dying, not healing — fewer hepatocytes to release ALT, but also fewer to make clotting factors) [6] |
Critical Exam Concept: Falling ALT with Worsening INR
"If AST/ALT is falling for a patient, along with worsening and prolongation of PT → have to keep fulminant hepatitis in mind" [6]. A falling ALT can be falsely reassuring — it may mean fewer hepatocytes are left to release enzymes. Always interpret ALT trends alongside INR.
| Parameter | AIH Findings | Interpretation |
|---|---|---|
| Bilirubin | Elevated (predominantly conjugated/direct) in active disease | Reflects impaired excretion by damaged hepatocytes; bilirubin may remain elevated for a long time even after clinical recovery — cholestatic phase [6] |
| ALP | Normal or mildly elevated | If disproportionately elevated → think cholestatic disease (PBC, PSC) or overlap syndrome |
| GGT | Normal or mildly elevated | GGT is an inducible enzyme — elevated by alcohol, drugs (phenytoin, carbamazepine), fatty liver, even without structural liver disease [8] |
The ALP:AST ratio is a key component of the IAIHG scoring system:
- ALP:AST < 1.5 → favours AIH (hepatitic pattern) → +2 points
- ALP:AST > 3.0 → favours cholestatic disease → −2 points
4.2 Immunological Investigations
| Immunoglobulin | AIH Pattern | Why? |
|---|---|---|
| ↑ IgG | Characteristic of AIH | Polyclonal B-cell activation in a chronic Th1/Th17-driven response produces IgG predominantly |
| Normal IgM | Normal in AIH | ↑ IgM = PBC (reflects different immune mechanism — innate immune activation, macrophage-driven) |
| Normal IgA | Normal in AIH | ↑ IgA = Alcoholic hepatitis (mucosal immune activation from alcohol-induced gut barrier dysfunction) |
"Immunoglobulin pattern in different liver diseases: ↑ IgG = Autoimmune hepatitis; ↑ IgM = Primary biliary cholangitis (PBC); ↑ IgA = Alcoholic hepatitis" [3]
The teaching clinic case: "IgG 2450 mg/dL (819–1725), IgM 200 mg/dL (70–386), IgA 176 mg/dL (55–307) → suspect autoimmune hepatitis" [1] — the IgG is elevated above the upper limit of normal while IgM and IgA are normal. This is the classic pattern.
| Autoantibody | Target Antigen | AIH Type | Sensitivity | Specificity | Notes |
|---|---|---|---|---|---|
| ANA | Nuclear antigens (non-specific) | Type 1 | ~75% | Low | Can be positive in healthy individuals, MASLD, other AI diseases. Titre ≥ 1:80 is more meaningful. |
| ASMA | F-actin (smooth muscle) | Type 1 | ~70% | Moderate | ASMA titres > 1:320 generally reflects the presence of anti-actin antibodies (AAA) and can serve as a surrogate marker [3] |
| Anti-actin (AAA) | F-actin filaments | Type 1 | ~40–70% | Higher than ASMA | IgG anti-F-actin antibodies detected by ELISA appear to be more sensitive than ASMA detected by immunofluorescence [3] |
| Anti-LKM1 | CYP2D6 (cytochrome P450IID6) | Type 2 | High for Type 2 | High | Antibodies directed at an epitope of CYP2D6 [3] |
| Anti-LC1 | Formiminotransferase cyclodeaminase | Type 2 | Lower | Moderate | May be the sole marker in some Type 2 cases |
| Anti-SLA/LP | UGA suppressor tRNA-associated protein | Both (originally called Type 3) | 10–30% | Most specific for AIH | Present in 10–30% of both Type 1 and 2 autoimmune hepatitis [3]; if positive, essentially confirms AIH |
| Atypical pANCA | Various nuclear antigens (not MPO) | Type 1 | ~60–90% | Low | Also seen in PSC and UC |
| AMA | Pyruvate dehydrogenase complex (M2) | Negative in AIH (if positive → PBC or overlap) | — | Highly specific for PBC | If AMA positive in a patient with AIH features → consider overlap syndrome. AMA positivity in the IAIHG score gives −4 points |
"Anti-smooth muscle/anti-F actin → type 1; anti-liver kidney microsomal-1 → type 2; anti-liver soluble antigen → type 3; (by experience → type 4 = no antibodies)" [1]
Practical interpretation of autoantibody results:
- A positive ANA alone at low titre (1:40) is insufficient — this can be found in healthy people.
- ANA 1/1080, Anti-smooth muscle Ab positive with elevated IgG → highly suggestive of AIH [1].
- Negative autoantibodies do not exclude AIH — up to 10–20% of AIH patients are "seronegative" (Type 4 by Prof. Yuen's clinical experience [1]). In such cases, biopsy is critical.
"Anti-mitochondrial antibody (AMA): typically seen in primary biliary cholangitis (cirrhosis) (PBC). Atypical perinuclear antineutrophil cytoplasmic antibodies (pANCA): typically seen in primary sclerosing cholangitis and ulcerative colitis." [3]
This is the mandatory first step — you cannot diagnose AIH without excluding viral causes:
| Test | Target | Interpretation |
|---|---|---|
| HBsAg | Chronic HBV | Must be negative to diagnose AIH (though co-existent AIH + HBV is possible) |
| Anti-HBc (total) | Past/current HBV exposure | If positive, further characterise with IgM anti-HBc and HBV DNA |
| IgM anti-HBc | Acute HBV or acute flare of chronic HBV | Can mean two things: acute infection OR acute flare of chronic infection [4] |
| Anti-HCV | HCV exposure | Hard to catch the acute phase unless you have had a needlestick injury [4] |
| HCV RNA | Active HCV replication | If anti-HCV positive, confirm with HCV RNA (PCR) |
| IgM anti-HAV | Acute HAV | Use IgM, not total/IgG (half of us will have positive IgG for Hep A — such a common virus [4]) |
| IgM anti-HEV | Acute HEV | Especially in endemic areas or post-travel |
"HBsAg negative, anti-HCV negative" → in the teaching clinic case, this was the prerequisite before proceeding to autoimmune workup [1]
| Test | Condition Excluded | Key Values |
|---|---|---|
| Serum ceruloplasmin | Wilson's disease | < 20 mg/dL is suspicious |
| 24h urinary copper | Wilson's disease | > 40 μg/day in adults is suspicious; > 100 μg/day strongly suggestive |
| Slit-lamp exam for Kayser-Fleischer rings | Wilson's disease | Present in ~95% with neurological Wilson's, ~50% with hepatic Wilson's |
| Serum iron, TIBC, transferrin saturation, ferritin | Haemochromatosis | Transferrin saturation > 45% = screen positive |
| HFE genotyping | Hereditary haemochromatosis | C282Y homozygosity diagnostic |
| Serum α1-antitrypsin level | α1-antitrypsin deficiency | Low level; confirm with phenotyping (PiZZ) |
This metabolic screen is essential in patients aged < 40 presenting with unexplained chronic hepatitis [5]
4.5 Liver Biopsy
Liver biopsy is central to the diagnosis of AIH — it provides histological confirmation and helps assess disease activity and fibrosis stage.
"± Liver biopsy: to confirm diagnosis" [2] "Liver biopsy may be required" [16]
- "Indicated in patients if the diagnosis is unclear or to assess disease activity prior to initiating treatment" [3]
- When autoantibodies are negative but clinical suspicion remains high (seronegative AIH)
- To distinguish AIH from overlap syndromes (AIH-PBC, AIH-PSC)
- To stage fibrosis (though FibroScan can also do this non-invasively)
- "Treatment may not be required in asymptomatic patients with normal or near-normal serum aminotransferase and IgG level who have minimal necroinflammatory activity on liver biopsy" [3] — so biopsy results can influence treatment decisions
| Finding | Description | Significance |
|---|---|---|
| Interface hepatitis | Inflammatory infiltrate at the portal-periportal junction breaching the limiting plate | Hallmark lesion of AIH; reflects active immune-mediated hepatocyte destruction [3] |
| Lymphoplasmacytic infiltrate | Lymphocytes and plasma cells in portal tracts extending into lobules | Plasma cells infiltrating the liver → specific feature of autoimmune hepatitis [7] |
| Hepatocyte rosette formation | Hepatocytes arranged in rosette-like clusters | Regenerative response; characteristic but not pathognomonic |
| Emperipolesis | Active penetration of one intact cell by a lymphocyte | Relatively specific for AIH |
| Bridging necrosis / Multiacinar necrosis | Necrosis connecting portal-portal or portal-central areas | Indicates severe disease activity; an indication for treatment [1] |
| Fibrosis → Cirrhosis | Progressive fibrosis with regenerative nodules | "Fibrosis is present in all forms of autoimmune hepatitis which connects portal and central areas (bridging) and ultimately leads to cirrhosis" [3] |
What histology is NOT AIH:
- Bile duct destruction, granulomas → think PBC
- Large duct involvement, periductal fibrosis ("onion-skinning") → think PSC
- Steatosis, ballooning → think MASLD/NASH (though can co-exist)
- "Histological features [of Wilson's] are similar to autoimmune hepatitis and non-alcoholic steatohepatitis" [12] — this is why biochemical exclusion of Wilson's is needed before interpreting biopsy
Teaching clinic histology slides: "A = normal liver, B, C = lymphocytes infiltrating into parenchyma, D = cirrhotic nodules → later finding" [7]
4.6 Additional Investigations
- First-line imaging for liver disease workup
- In AIH: may show hepatomegaly (if active inflammation), signs of cirrhosis (nodular surface, splenomegaly, ascites), or may be entirely normal
- Main role is to exclude biliary obstruction (dilated ducts) and screen for HCC (focal lesions)
- "Only when there is a physical entity causing the pathology, imaging is helpful" [8] — for AIH, the diagnosis is biochemical and histological, not radiological
- Check in the context of cirrhosis surveillance
- HCC is rare in autoimmune hepatitis [7] — but if AIH has progressed to cirrhosis, HCC surveillance is still recommended (though at lower intensity than for HBV-related cirrhosis)
- May show pancytopenia if cirrhosis with hypersplenism is present
- Macrocytic anaemia if concurrent B12/folate deficiency or alcohol use
- Normocytic anaemia of chronic disease
- Shows a polyclonal elevation of the gamma band (broad-based hypergammaglobulinaemia)
- Distinguished from a monoclonal spike (seen in myeloma, which is a different cause of elevated globulins)
- This is how the "hyperglobulinaemia" of AIH appears electrophoretically
Here is the step-by-step approach a clinician in HK would use when AIH is suspected:
| Step | Investigation | What You're Looking For | If Positive for AIH |
|---|---|---|---|
| 1 | LFT | Hepatitic pattern (↑ALT/AST, normal-mild ↑ALP) | Check — ALT typically > AST |
| 2 | Viral serology | HBsAg, anti-HCV, IgM anti-HAV, IgM anti-HEV | All negative |
| 3 | Drug/alcohol history | Culprit drug, TCM/herb, alcohol intake | No culprit, non/minimal drinker |
| 4 | Immunoglobulins | IgG level | Elevated (> ULN, ideally > 1.1× ULN) |
| 5 | Autoantibodies | ANA, ASMA, anti-LKM1, anti-SLA/LP | At least one positive at meaningful titre |
| 6 | Metabolic screen | Ceruloplasmin, iron studies, α1-AT | All normal |
| 7 | Liver biopsy | Interface hepatitis, plasma cells, rosettes | Typical or compatible histology |
| 8 | Apply simplified score | Sum of autoantibodies + IgG + histology + negative viral | ≥ 7 = definite; ≥ 6 = probable |
| 9 | Initiate treatment | Corticosteroids ± azathioprine | Response to treatment further supports diagnosis |
Workup for marked/moderate transaminase elevation: "Ig pattern, ANA, anti-smooth muscle Ab, serum ceruloplasmin and urine copper, liver biopsy if all negative" [5]
Based on the GI Data Interpretation and LFT lecture material [4][8][16][17]:
| Scenario on Exam | Key Interpretation |
|---|---|
| ALT/AST elevated, all viral markers negative, elevated IgG, ANA positive | Suspect AIH → apply simplified scoring |
| ALT > AST with elevated IgG | Consistent with AIH (most primary liver diseases have ALT > AST) |
| AST > ALT | Four causes: alcoholic hepatitis, HCC, CHF, ischaemic hepatitis [8] — NOT typical AIH |
| Isolated ↑GGT with normal ALP | Drug-induced, alcohol, fatty liver — GGT is an inducible enzyme [8] |
| ↑ALP + ↑GGT with normal ALT/AST | Cholestatic pattern → check AMA for PBC, MRCP for PSC [8] |
| Rapidly falling ALT/AST (> 1000 U/L per day) | Ischaemic hepatitis, paracetamol overdose, or cholangiohepatitis [8] — NOT AIH |
| Falling ALT with worsening INR | Fulminant liver failure — hepatocytes dying, cannot make clotting factors [6] |
High Yield Summary: Diagnosis of AIH
No single test is diagnostic — AIH diagnosis requires a composite approach:
- Hepatitic LFT pattern (↑ALT/AST, normal-mild ALP)
- Negative viral markers (HBsAg, anti-HCV, IgM anti-HAV, IgM anti-HEV)
- Elevated IgG (with normal IgM and IgA)
- Positive autoantibodies (ANA/ASMA for Type 1; anti-LKM1 for Type 2; anti-SLA/LP most specific)
- Liver biopsy: interface hepatitis + plasma cell-rich infiltrate = hallmark
- Exclusion of drugs/alcohol/metabolic causes (Wilson's, haemochromatosis, α1-AT deficiency)
Simplified Scoring: ≥ 7 = definite, ≥ 6 = probable (4 variables: autoantibodies, IgG, histology, viral exclusion)
Immunoglobulin pattern: ↑IgG = AIH, ↑IgM = PBC, ↑IgA = Alcoholic hepatitis
Histology hallmarks: Interface hepatitis, lymphoplasmacytic infiltrate (especially plasma cells), rosettes, emperipolesis
Response to corticosteroids further supports the diagnosis
Active Recall - Diagnostic Criteria and Investigations for AIH
References
[1] Lecture slides: Teaching Clinic - Non-viral chronic liver diseases (Prof. Yuen Man Fung) 2.pdf (p.3, p.5–6) [2] Senior notes: Maksim Medicine Notes.pdf (p.150, Autoimmune hepatitis section) [3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.730–733, Autoimmune hepatitis) [4] Senior notes: Block A - Gastrointestinal Data Interpretation.pdf (p.2) [5] Senior notes: Ryan Ho Fundamentals.pdf (p.305) [6] Senior notes: Block A - Jaundice after raw oysters_ acute hepatitis.pdf (p.2) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.1–2) [8] Senior notes: Block A - Introduction to GI_Hepatology investigations (LFT, Endoscopy).pdf (p.5–6, p.10) [12] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p.386) [13] Senior notes: Block A - Gastroenterology Interactive Tutorial.pdf (p.2) [16] Lecture slides: Gastroenterology Hepatology Introduction to GI/Hepatology investigations from the abnormal.pdf (p.49) [17] Senior notes: Learning_Points_All_Lectures.txt (Gastroenterology/Hepatology section)
Management of Autoimmune Hepatitis
The management of AIH rests on three pillars:
- Immunosuppressive therapy directed at the autoimmune-mediated inflammation — this is the cornerstone and what makes AIH a treatable cause of chronic liver disease
- Prevention and treatment of corticosteroid side effects — because the drugs we use can be as problematic as the disease itself if used carelessly
- Prevention and treatment of cirrhosis-related complications — if the patient has already developed cirrhosis at diagnosis [5]
The fundamental logic is straightforward: AIH is driven by an overactive immune system attacking hepatocytes. Suppress the immune system → stop the attack → liver heals → fibrosis progression halts or even reverses. Without treatment, most patients eventually develop cirrhosis [2].
Critical Concept: AIH is Treatable
Unlike many other causes of chronic liver disease (e.g., MASLD where we have limited pharmacotherapy, HBV where we suppress but rarely cure), AIH responds dramatically to immunosuppression. Missing this diagnosis means missing a highly treatable condition.
Not every patient with AIH requires immediate immunosuppression. The decision to treat depends on disease severity.
"Who and when to treat?" [1] "ALT > 10× upper limit of normal" [1] "ALT > 5× upper limit of normal and serum γ-globulin ≥ 2× upper limit of normal" [1] "Histologic features of bridging necrosis or multiacinar necrosis" [1] "Symptomatic patients" [1]
These are the AASLD (American Association for the Study of Liver Diseases) indications, and they are the standard taught at HKUMed:
| Indication | Rationale |
|---|---|
| ALT > 10× ULN | Severe hepatocyte necrosis — high risk of progression to fibrosis/cirrhosis and liver failure if untreated |
| ALT > 5× ULN AND serum γ-globulin ≥ 2× ULN | Moderate-severe disease activity with significant immune activation |
| Bridging necrosis or multiacinar necrosis on histology | Poor prognostic histological features — necrosis connecting portal-portal or portal-central areas predicts rapid progression to cirrhosis |
| Symptomatic patients (fatigue, jaundice, arthralgia) | Symptoms indicate clinically significant disease activity |
What about patients with milder disease?
"Can treat even if 2–3 times elevation → prevent progression" [7]
This is a nuanced point from Prof. Yuen Man Fung's teaching clinic: even patients with mild transaminase elevation (2–3× ULN) may benefit from treatment to prevent long-term progression. The threshold for treatment has been lowering over time as evidence accumulates that even low-grade inflammation causes cumulative fibrosis over decades.
"Treatment may not be required in asymptomatic patients with normal or near-normal serum aminotransferase and IgG level who have minimal necroinflammatory activity on liver biopsy" [3] — these are the truly quiescent patients where watchful waiting with close monitoring is reasonable.
Before starting immunosuppression, several critical checks must be performed:
| Check | Why? |
|---|---|
| Check TB | Steroids can reactivate latent tuberculosis → perform chest X-ray and consider IGRA/Mantoux test |
| Check HBV/HCV | "Check TB, HBV/HCV" [2]. Steroids cause HBV reactivation — occult Hep B is bad when you are prescribing steroids or immunosuppressants [4]. If HBsAg positive or even anti-HBc positive, prophylactic antiviral therapy is needed |
| Check TPMT before azathioprine | "Monitoring requires TPMT — 1 in 300 with deficiency of this enzyme, most azathioprine will turn into active form → toxicity, myelosuppression. Enzyme normally helps to turn drug into inactive form" [7] |
| Check NUDT15 before azathioprine | "NUDT15 also important" [7] — NUDT15 deficiency is more common in the Asian/HK population [19] and predisposes to thiopurine-related myelosuppression |
| Check for concurrent xanthine oxidase inhibitors | "Is the patient taking any xanthine oxidase inhibitors (e.g., gout meds such as allopurinol, febuxostat) → as XO is crucial for the conversion of active 6-MP into 6-TU" [19] — concurrent use dramatically increases azathioprine toxicity |
| Bone density baseline | Long-term steroids cause osteoporosis → obtain baseline DEXA if planning prolonged steroid use |
| Screen for diabetes, hypertension | Steroids worsen glucose metabolism and blood pressure |
| Vaccination | Update vaccinations (especially influenza, pneumococcal, hepatitis A/B) before starting immunosuppression |
HBV Reactivation Risk — A HK-Specific Concern
In Hong Kong's high HBV prevalence setting, EVERY patient about to start steroids or immunosuppression must have HBV serology checked (HBsAg, anti-HBs, anti-HBc). If HBsAg positive → start prophylactic entecavir/tenofovir. If HBsAg negative but anti-HBc positive (past infection / occult HBV) → monitor HBV DNA closely or start prophylactic antiviral depending on the intensity of immunosuppression. "Just start prophylactic antiviral therapy → irrespective of baseline HBV DNA levels. Superior and safer than monitoring for reactivation and treating when it occurs." [18]
4. Treatment Regimens
"Current 1st line therapy (gold standard): Prednisone + azathioprine" [1]
| Phase | Predniso(lo)ne | Azathioprine |
|---|---|---|
| Induction | 15–30 mg/day (combination) or 20–60 mg/day (monotherapy) | 50–100 mg/day |
| Maintenance | 5–10 mg/day (combination) | 50–150 mg/day |
Teaching clinic regimen table: [1]
Regimen Single-drug Therapy Combination Therapy Initial Prednisone 20–60 mg/day Prednisone 15–30 mg/day + Azathioprine 50–100 mg/day Maintenance Prednisone 20–60 mg/day or Azathioprine 50–200 mg/day Prednisone 5–10 mg/day + Azathioprine 50–150 mg/day
HK-specific dosing approach:
"In HK we can do 0.5 mg/kg/day" [7] — this is the starting steroid dose used locally, somewhat lower than some Western guidelines (which start at 1 mg/kg/day in some protocols).
Why combination therapy is preferred:
- Azathioprine has a steroid-sparing effect — you can use a lower dose of steroids, thus reducing steroid side effects (Cushingoid features, osteoporosis, diabetes, hypertension, cataracts, infections, etc.)
- The combination is as effective as high-dose steroid monotherapy but with significantly fewer steroid-related adverse effects
The treatment timeline:
"Start steroid first → Stop steroid within 4 to 12 weeks is the aim → After taper off, use azathioprine for lifelong therapy (decades)" [7]
The practical approach:
- Start predniso(lo)ne at induction dose
- Add azathioprine at ~50 mg/day (once TPMT/NUDT15 checked), uptitrate to 1–2 mg/kg/day based on response
- Taper steroids gradually over 4–12 weeks as transaminases normalise
- Maintain on azathioprine monotherapy (or low-dose steroid + azathioprine) for the long term — typically years to decades
"Reasons for monotherapy with prednisone only include: Cytopenia, TPMT deficiency, malignancy, pregnancy" [1]
| Indication for Monotherapy | Rationale |
|---|---|
| Cytopenia | Azathioprine is myelosuppressive — adding it to an already cytopenic patient risks severe bone marrow failure |
| TPMT deficiency | Cannot metabolise azathioprine safely → accumulation of toxic 6-TGN metabolites → life-threatening myelosuppression [7] |
| Malignancy | Azathioprine is a purine analogue with theoretical carcinogenic risk (especially lymphoma); avoid in patients with active malignancy |
| Pregnancy | Although azathioprine is used in pregnancy in IBD and transplant settings, some centres prefer steroid monotherapy; practice varies |
Monotherapy requires higher steroid doses for both induction and maintenance, leading to more steroid-related complications.
5. Understanding the Drugs: From First Principles
Name breakdown: "Predniso-" derives from "pregnane" (a steroid skeleton) + "-olone" (a ketone group). Prednisolone is the active form; prednisone is the prodrug that is converted to prednisolone in the liver.
Mechanism in AIH:
- Corticosteroids bind to intracellular glucocorticoid receptors → translocate to the nucleus → suppress transcription of pro-inflammatory genes (IL-1, IL-2, IL-6, TNF-α, IFN-γ)
- Reduce T-cell activation, proliferation, and cytotoxicity → directly counteract the CD4/CD8 T-cell-mediated hepatocyte destruction that drives AIH
- Reduce B-cell activation → lower immunoglobulin production → IgG falls
- Reduce expression of MHC class II molecules on APCs → less antigen presentation → less immune activation
Why steroids work so well in AIH: The disease is fundamentally driven by adaptive immune activation (T-cells and B-cells). Steroids are broad-spectrum immunosuppressants that hit every component of this cascade.
Key side effects (dose- and duration-dependent):
- Metabolic: hyperglycaemia/diabetes, weight gain, dyslipidaemia, Cushingoid habitus
- Musculoskeletal: osteoporosis (→ fractures), avascular necrosis, myopathy
- Immunological: increased infection risk (especially TB reactivation, fungal infections)
- Ophthalmic: cataracts, glaucoma
- Dermatological: skin thinning, striae, easy bruising, acne
- Psychiatric: insomnia, mood disturbance, psychosis
- Cardiovascular: hypertension, fluid retention
- GI: peptic ulceration (especially with concurrent NSAIDs)
Prednisolone vs Prednisone in liver disease: In severe liver disease or cirrhosis, the liver's capacity to convert prednisone (inactive) → prednisolone (active) may be impaired. Therefore, prednisolone is generally preferred in patients with significant liver dysfunction.
Name breakdown: "Aza-" = nitrogen-containing (a nitrogen atom replaces a carbon in the purine ring); "-thio-" = sulphur-containing; "-purine" = purine analogue. So azathioprine is a nitrogen- and sulphur-modified purine analogue.
Mechanism:
- Azathioprine is a prodrug — it is converted to 6-mercaptopurine (6-MP) non-enzymatically, then to its active metabolite 6-thioguanine nucleotides (6-TGN) via the enzyme HPRT
- 6-TGN incorporates into DNA during replication → causes DNA strand breaks and apoptosis of rapidly dividing lymphocytes
- Selectively suppresses T-cell and B-cell proliferation → reduces the autoimmune attack on hepatocytes
- Onset of action is slow (~3 months for full effect) [19] → hence you need steroids for the initial rapid control
Why we check TPMT and NUDT15 before starting:
- TPMT (thiopurine S-methyltransferase): converts 6-MP → 6-MMP (inactive metabolite). If TPMT is deficient, 6-MP is shunted towards the HPRT pathway → excessive 6-TGN accumulation → toxicity, myelosuppression [7]
- NUDT15: degrades 6-TGN into inactive metabolites. If NUDT15 is deficient, 6-TGN accumulates → myelosuppression. NUDT15 deficiency is more common in the Asian/HK population [7][19]
- Xanthine oxidase (XO): converts 6-MP → 6-thiouric acid (6-TU, inactive). If a patient is taking allopurinol or febuxostat (XO inhibitors for gout), this pathway is blocked → 6-MP accumulates → toxicity [19]
"Azathioprine can be broken down via three mechanisms → hence, any defect of these mechanisms can lead to excessive and toxic accumulation of the azathioprine metabolite, resulting in bone marrow suppression / neutropenic fever" [19]
Key side effects:
- Myelosuppression (leukopenia, neutropenia, thrombocytopenia) — the most dangerous
- Hepatotoxicity (paradoxical)
- Pancreatitis (~3–5%, usually early in treatment)
- GI intolerance (nausea, vomiting)
- Increased infection risk
- Small increased risk of lymphoma with long-term use
Monitoring on azathioprine:
- CBC (complete blood picture) at regular intervals — initially every 1–2 weeks, then monthly
- LFT periodically (for drug-induced hepatotoxicity)
Budesonide is a topically active corticosteroid with high first-pass metabolism in the liver (> 90% hepatic extraction). In theory, this means:
- High local steroid concentration in the liver → effective for AIH
- Low systemic bioavailability → fewer systemic steroid side effects
Indication: Can be used as an alternative to prednisolone in non-cirrhotic AIH patients to reduce steroid side effects.
Contraindication: Should NOT be used in patients with cirrhosis — in cirrhosis, portal-systemic shunting bypasses the liver, so budesonide enters the systemic circulation directly, negating the first-pass advantage and causing systemic steroid effects.
Name breakdown: "Myco-" = derived from a fungal compound (Penicillium); "phenolate" = phenolic chemical group; "mofetil" = morpholinoethyl ester (prodrug form).
Mechanism: Prodrug → converted to mycophenolic acid (MPA) → inhibits inosine monophosphate dehydrogenase (IMPDH) → blocks de novo purine synthesis → selectively inhibits lymphocyte proliferation (lymphocytes uniquely depend on de novo purine synthesis, unlike other cells that can use salvage pathways).
Role in AIH:
"Mycophenolate mofetil is being touted to replace azathioprine, since it may be safer — becoming the first line" [7]
- Used as second-line or increasingly as alternative first-line to azathioprine
- Particularly useful in:
- Patients intolerant to azathioprine (e.g., pancreatitis, hepatotoxicity)
- Patients with incomplete response to azathioprine
- TPMT or NUDT15 deficient patients
- Dose: typically 1–2 g/day in divided doses
- Contraindicated in pregnancy (teratogenic — unlike azathioprine which has more safety data in pregnancy)
| Agent | Mechanism | When Used | Key Considerations |
|---|---|---|---|
| Tacrolimus | Calcineurin inhibitor → blocks IL-2 transcription → inhibits T-cell activation | Refractory AIH | Nephrotoxic; monitor drug levels |
| Ciclosporin | Calcineurin inhibitor (same pathway as tacrolimus) | Refractory AIH, especially acute severe AIH unresponsive to steroids | Nephrotoxic; hirsutism, gingival hyperplasia |
| 6-Mercaptopurine | Active metabolite of azathioprine | AZA-intolerant patients (some tolerate 6-MP directly) | Same TPMT/NUDT15 considerations |
| Rituximab | Anti-CD20 monoclonal antibody → depletes B-cells | Severe refractory AIH | HBV reactivation risk; infusion reactions |
| Infliximab | Anti-TNF-α monoclonal antibody | Case reports only; used in refractory disease | Can itself trigger drug-induced AIH (ironic) |
"Monitor response to steroids: globulin, IgG and ALT (DO NOT expect autoantibodies to drop)" [1]
This is a crucial teaching point:
| Parameter | Role in Monitoring | Expected Change with Treatment |
|---|---|---|
| ALT/AST | Disease activity marker | Should normalise within weeks to months |
| Serum IgG / γ-globulin | Immune activation marker | Should normalise; correlates with disease activity |
| Serum albumin | Synthetic function | Should improve if initially impaired |
| PT/INR | Synthetic function | Should normalise |
| Autoantibody titres | DO NOT correlate well with disease activity [5] | Do NOT expect autoantibodies to drop [1] — this is a common misconception. ANA/ASMA titres may remain positive even in complete remission |
Monitoring schedule: AST/ALT, bilirubin, γ-globulin/IgG every 3–6 months [5]
Treatment endpoints:
| Endpoint | Definition |
|---|---|
| Complete biochemical remission | Normal ALT + normal IgG for ≥ 2 years on therapy |
| Incomplete response | Some improvement but failure to achieve complete normalisation despite adequate therapy (occurs in ~15–20%) |
| Treatment failure | Worsening or no improvement despite adequate therapy (occurs in ~5–10%) |
| Drug intolerance | Side effects that mandate dose reduction or drug cessation |
| Histological remission | Liver biopsy shows resolution of interface hepatitis — this is the gold standard endpoint but not always obtained |
Can you ever stop treatment?
This is a common patient question. The answer is: sometimes, but relapse rates are high.
-
A withdrawal trial can be considered after:
- ≥ 3 years of sustained biochemical remission (normal ALT + normal IgG)
- Ideally confirmed by liver biopsy showing resolution of interface hepatitis
- If biopsy still shows active inflammation despite normal bloods, do NOT withdraw
-
Relapse rate after withdrawal: 70–80% — the majority of patients relapse, often within 12 months of stopping therapy
-
After relapse, patients usually need lifelong treatment with azathioprine (or alternative)
-
"After taper off, use azathioprine for lifelong therapy (decades)" [7]
9. Management of Special Situations
- Start high-dose IV methylprednisolone (e.g., 60 mg IV daily) immediately if clinical suspicion is high — do not wait for biopsy results
- Assess response within 7–14 days: if MELD score improves and INR/bilirubin trending down → continue
- If no response within 7–14 days → urgent referral for liver transplantation assessment
- In fulminant liver failure, liver transplantation is the final line → after exhausting all other treatments [15]
- Treatment principles remain the same (steroids + azathioprine)
- Additional management of cirrhosis-related complications: variceal surveillance (OGD), HCC screening (6-monthly USG ± AFP), ascites management, hepatic encephalopathy prevention
- HCC is rare in autoimmune hepatitis [7] — but surveillance is still recommended once cirrhosis is established
- Consider liver transplantation for decompensated cirrhosis refractory to medical therapy
- AIH often improves during pregnancy (immunotolerant state) and flares postpartum
- Azathioprine is generally continued during pregnancy — extensive safety data from IBD and transplant populations. Category D but clinical benefit outweighs theoretical risk in most cases.
- Prednisolone is safe in pregnancy
- MMF is absolutely contraindicated (teratogenic — causes ear, facial, limb, cardiac, and oesophageal malformations)
- Monitor closely in the postpartum period for flare
| Overlap | Treatment |
|---|---|
| AIH-PBC | UDCA (for PBC component) + immunosuppression (for AIH component) |
| AIH-PSC | Immunosuppression + UDCA (though benefit of UDCA in PSC is limited); may eventually require transplant |
- AIH can recur after liver transplantation (~20–40%)
- De novo AIH can develop in transplanted livers
- Managed with standard immunosuppressive regimens (often already on tacrolimus/MMF for rejection prophylaxis)
| Situation | Regimen |
|---|---|
| Standard first-line | Predniso(lo)ne + azathioprine [1] |
| Contraindication to AZA | Predniso(lo)ne monotherapy [1] |
| AZA intolerance (e.g., pancreatitis) | Predniso(lo)ne + MMF |
| Non-cirrhotic, steroid side effect concerns | Budesonide + azathioprine |
| Cirrhotic (do NOT use budesonide) | Predniso(lo)ne + azathioprine |
| Refractory disease | Tacrolimus, ciclosporin, rituximab |
| Fulminant liver failure, no treatment response | Liver transplantation |
| Pregnancy | Continue prednisolone ± azathioprine; contraindicate MMF |
High Yield Summary: Management of AIH
Indications for treatment (AASLD): ALT > 10× ULN; ALT > 5× ULN + γ-globulin ≥ 2× ULN; bridging/multiacinar necrosis; symptomatic patients. Can also treat milder disease to prevent progression.
Pre-treatment checks: TPMT, NUDT15 (especially in Asian populations), HBV serology (start antiviral prophylaxis if HBsAg+ or anti-HBc+), TB screening, xanthine oxidase inhibitor co-administration.
First-line: Predniso(lo)ne + azathioprine. Start steroid, taper over 4–12 weeks, maintain on azathioprine for years/decades.
Monotherapy indications: Cytopenia, TPMT deficiency, malignancy, pregnancy.
Monitoring: ALT, IgG, γ-globulin every 3–6 months. Autoantibody titres do NOT correlate with disease activity.
Second-line: Mycophenolate mofetil (increasingly used, may replace AZA). Tacrolimus, ciclosporin for refractory cases.
Relapse rate: 70–80% after treatment withdrawal → most patients need lifelong therapy.
Budesonide: Only in non-cirrhotic patients (first-pass metabolism lost with cirrhotic shunting).
HBV prophylaxis: Mandatory in HK — check before any immunosuppression.
Active Recall - Management of Autoimmune Hepatitis
References
[1] Lecture slides: Teaching Clinic - Non-viral chronic liver diseases (Prof. Yuen Man Fung) 2.pdf (p.10–11) [2] Senior notes: Maksim Medicine Notes.pdf (p.150, Autoimmune hepatitis section) [3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.733, AIH histology and treatment indications) [4] Senior notes: Block A - Gastrointestinal Data Interpretation.pdf (p.4, occult HBV and immunosuppression) [5] Senior notes: Ryan Ho GI.pdf (p.281, AIH management and monitoring) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.1–2) [15] Senior notes: Block A - A jaundiced and incoherent patient_ liver failure.pdf (p.24) [18] Senior notes: Block A - I am a hepatitis B carrier.pdf (p.70, HBV reactivation prevention) [19] Senior notes: Block A - Chronic diarrhoea_ irritable bowel syndrome and inflammatory bowel disease.pdf (p.45, azathioprine pharmacology)
Complications of Autoimmune Hepatitis
The complications of AIH can be divided into two broad categories:
- Disease-related complications — consequences of the autoimmune hepatitis itself (primarily progressive liver disease)
- Treatment-related complications — consequences of the immunosuppressive therapy used to manage AIH
Understanding these complications requires appreciating two parallel timelines: the natural history of untreated/undertreated AIH leading to cirrhosis and its downstream consequences, and the iatrogenic burden of decades of immunosuppression.
"Treatment of Autoimmune Hepatitis — 3 major components: Specific therapy directed at the auto-immune mediated inflammation (Immunosuppressives), Prevention and treatment of corticosteroid side-effects, Prevention and treatment of cirrhosis-related complications" [1]
1. Disease-Related Complications
This is the most common and most important complication. The fundamental pathway is:
Chronic inflammation → interface hepatitis → bridging necrosis → progressive fibrosis (F1 → F2 → F3 → F4) → cirrhosis
"Fibrosis is present in all forms of autoimmune hepatitis which connects portal and central areas (bridging) and ultimately leads to cirrhosis by architectural distortion of the hepatic lobule and appearance of regenerative nodules" [3]
Why does inflammation cause fibrosis? Hepatocyte necrosis activates hepatic stellate cells (HSCs), which transform from quiescent vitamin A-storing cells into myofibroblast-like cells. These activated HSCs deposit extracellular matrix (primarily type I and III collagen) in the space of Disse. With repeated and chronic injury, collagen accumulates faster than it is degraded → progressive fibrosis → architectural distortion → regenerative nodules → cirrhosis.
Progression rates by AIH type [5]:
- Type 1: approximately 45% progress to cirrhosis
- Type 2: approximately 82% progress to cirrhosis (more aggressive, less treatment-responsive)
- Type 3: approximately 75% progress to cirrhosis
Prognosis without treatment:
"Severe untreated AIH can be associated with a very high mortality of up to 50% after 3–5 years of diagnosis" [1][3]
"With correct treatment, life-expectancy can approach that of age- and gender-matched controls" [1]
This dramatic difference in outcomes underscores why early diagnosis and treatment are critical.
Can fibrosis reverse? Yes — with effective immunosuppression, fibrosis regression has been demonstrated, especially in earlier stages (F1–F3). Even in some cirrhotic patients, there is evidence of histological improvement with treatment [20].
Key Prognostic Concept
AIH is one of the few causes of chronic liver disease where treatment can genuinely alter the natural history — from 50% mortality at 3–5 years (untreated) to near-normal life expectancy (treated). This makes missing the diagnosis tragic.
1.2 Complications of Cirrhosis (Decompensation)
Once cirrhosis develops, the patient is at risk of all the standard complications of cirrhosis. The transition from compensated to decompensated cirrhosis is a critical prognostic milestone.
"Poor survival once becomes decompensated" [4]
"6 associated complications of liver failure: Infections, Variceal bleeding, Ascites / Spontaneous bacterial peritonitis, Hepatorenal syndrome, Hepatic encephalopathy, (Coagulopathy), (Hepatocellular carcinoma)" [15]
"Portal hypertension contributes to the majority of complications, but not all → HE, HCC, liver failure are the exceptions" [21]
The complications can be organised by underlying mechanism:
Cirrhosis increases intrahepatic vascular resistance (architectural distortion compresses sinusoids and hepatic venules) → back-pressure in the portal venous system → portal hypertension (portal venous pressure gradient > 5 mmHg; clinically significant at > 10 mmHg).
| Complication | Mechanism | Clinical Features | Management |
|---|---|---|---|
| Oesophageal / gastric varices and variceal bleeding | Portal hypertension → formation of portosystemic collaterals, most importantly at the gastro-oesophageal junction where submucosal veins dilate into varices → thin-walled, engorged veins susceptible to rupture | Haematemesis, melaena, haemodynamic instability | Screening OGD every 2–3 years; prophylactic banding or non-selective beta-blockers (propranolol/carvedilol); acute bleeding: resuscitation, variceal band ligation, octreotide, prophylactic antibiotics before banding [15] |
| Ascites | Portal hypertension → splanchnic vasodilatation → effective hypovolaemia → RAAS activation → sodium and water retention; simultaneously, hydrostatic back-pressure pushes fluid into the peritoneal cavity; low albumin (reduced oncotic pressure) worsens transudation | Abdominal distension, shifting dullness, fluid thrill | Salt restriction, spironolactone ± furosemide, therapeutic paracentesis with albumin replacement, TIPS for refractory ascites |
| Spontaneous bacterial peritonitis (SBP) | Ascitic fluid is a good culture medium; bacterial translocation from gut (impaired gut barrier in cirrhosis) → infection of ascitic fluid without an obvious intra-abdominal source | Fever, abdominal pain, worsening encephalopathy in a cirrhotic patient with ascites; ascitic fluid neutrophil count ≥ 250/mm³ | Empirical IV ceftriaxone/cefotaxime; secondary prophylaxis with norfloxacin |
| Splenomegaly / hypersplenism | Passive congestion of spleen from portal hypertension → sequestration and destruction of blood cells | Pancytopenia (thrombocytopenia most prominent), palpable spleen | Usually no specific treatment; splenectomy rarely indicated |
| Complication | Mechanism | Clinical Features |
|---|---|---|
| Jaundice | Impaired bilirubin conjugation and excretion by failing hepatocytes | Progressive yellow discolouration of skin and sclerae |
| Coagulopathy | Impaired synthesis of clotting factors (all factors except vWF and factor VIII are liver-synthesised); additionally thrombocytopenia from hypersplenism and reduced thrombopoietin production | Prolonged PT/INR, easy bruising, bleeding |
| Hypoalbuminaemia | Impaired albumin synthesis | Peripheral oedema, ascites (reduced oncotic pressure contribution), muscle wasting |
| Hepatic encephalopathy (HE) | The failing liver cannot detoxify ammonia (normally converted to urea via the urea cycle) → hyperammonaemia → ammonia crosses the blood-brain barrier → astrocyte swelling (ammonia is converted to glutamine by glutamine synthetase in astrocytes, glutamine is osmotically active → cell swelling) → cerebral oedema, neurotoxicity | Confusion, personality change, asterixis (flapping tremor), fetor hepaticus, progressing to coma |
Precipitating factors for hepatic encephalopathy include: GI bleed (nitrogen load), sepsis, constipation, overdiuresis, excess paracentesis without adequate albumin replacement, sedatives, electrolyte imbalance (especially hypokalaemia — alkalosis promotes conversion of NH4+ to NH3 which crosses the BBB more readily), renal failure, dietary protein excess, TIPS [15]
- Mechanism: Advanced cirrhosis → severe splanchnic vasodilatation → marked effective hypovolaemia → intense renal vasoconstriction (mediated by RAAS, sympathetic nervous system, ADH) → pre-renal kidney failure without structural renal damage
- Two types:
- HRS-AKI (formerly Type 1): rapidly progressive (creatinine doubling in < 2 weeks); very poor prognosis
- HRS-CKD (formerly Type 2): slowly progressive; associated with refractory ascites
- Management: IV albumin + terlipressin (splanchnic vasoconstrictor); definitive treatment is liver transplantation
"Very common. Bacteria especially from the respiratory and urinary tract — Staph, strep, gram-negative rods. Bacteremia in up to 25% of fulminant hepatic failure patients. Fungal infection — especially Candida" [15]
"Mechanism: reticuloendothelial dysfunction and reduced opsonization. Liver failure → impaired ability to clear toxins. At the same time, production impaired meaning less production of opsonins such as complements → less bacteria tagged for phagocytosis" [15]
Cirrhotic patients are effectively immunocompromised because:
- Kupffer cell dysfunction → impaired hepatic clearance of bacteria from portal blood
- Reduced complement synthesis → less opsonisation
- Reduced immunoglobulin production → impaired humoral immunity
- Gut bacterial translocation → leaky gut barrier in cirrhosis allows bacteria to enter the portal and systemic circulation
"Primary HCC is thought to be a natural consequence of chronic hepatitis-cirrhosis disease progression and autoimmune hepatitis is not an exception to this hypothesis. Progression to HCC is relatively rare in autoimmune hepatitis." [3]
HCC is rare in autoimmune hepatitis [7]
Why is HCC rare in AIH compared to HBV/HCV?
- HBV has a direct oncogenic effect — HBV DNA integration into host genome causes insertional mutagenesis + HBx protein is a transactivator that promotes cell proliferation and inhibits p53. This means HBV can cause HCC even without cirrhosis [22].
- HCV promotes HCC through cirrhosis-dependent and cirrhosis-independent mechanisms (core protein interference with cell cycle regulation).
- AIH drives HCC risk only through the cirrhosis pathway (chronic inflammation → regenerative nodules → dysplastic nodules → HCC). Since AIH does not have a direct oncogenic mechanism, and since effective immunosuppression can slow or halt fibrosis progression, HCC risk is lower.
HCC surveillance in AIH: Despite the lower risk, guidelines still recommend surveillance in AIH patients who have developed cirrhosis — typically 6-monthly ultrasound ± AFP [20]. However, the threshold for surveillance is less stringent than for HBV, where surveillance begins even without cirrhosis in certain age groups.
Autoimmune liver diseases (autoimmune hepatitis, PBC, PSC) are listed as risk factors for HCC [22]
As discussed in clinical features, approximately 25% of AIH patients present acutely, and a small subset develop fulminant hepatic failure [2]. This is a direct complication of massive, uncontrolled autoimmune hepatocyte destruction. Key complications of acute liver failure include:
- Cerebral oedema (from hyperammonaemia → astrocyte swelling)
- Coagulopathy (loss of synthetic function)
- Sepsis (immunoparesis)
- Multi-organ failure
Management follows standard ALF protocols (ICU care, consider high-dose steroids for AIH-specific ALF, liver transplantation if no response).
Relapse is extremely common in AIH:
- After treatment withdrawal: 70–80% relapse rate
- After initial successful treatment: relapses can occur even on maintenance therapy
- Each relapse episode causes additional hepatocyte damage, accelerating fibrosis
"Stopping Tx early is associated with increased risk of relapse — usually only consider stopping after > 10 years of maintenance treatment" [5]
"Treatment of relapses: same Tx as initial Mx (induction + maintenance). S/S: development of fatigue, arthralgia and anorexia. Ix: ↑AST/ALT > 3× ULN and/or ↑serum γ-globulin > 2 g/dL associated with ↑histological activity" [5]
2. Treatment-Related Complications
These are dose- and duration-dependent. Since many AIH patients require prolonged steroid therapy (especially if azathioprine is contraindicated), steroid complications are a major clinical concern.
| System | Complication | Mechanism |
|---|---|---|
| Metabolic | Diabetes mellitus / hyperglycaemia | Steroids promote hepatic gluconeogenesis + peripheral insulin resistance |
| Weight gain / Cushingoid habitus (moon face, buffalo hump, truncal obesity) | Increased appetite + fat redistribution | |
| Dyslipidaemia | Altered lipid metabolism | |
| Musculoskeletal | Osteoporosis → fractures | Steroids inhibit osteoblast activity + promote osteoclast activity + reduce calcium absorption from gut + increase renal calcium excretion |
| Avascular necrosis (especially femoral head) | Impaired blood supply to bone (mechanism not fully understood — possibly fat emboli in subchondral vessels) | |
| Steroid myopathy (proximal weakness) | Catabolic effect on skeletal muscle protein | |
| Immune | Increased infection risk | Broad immunosuppression → opportunistic infections (TB reactivation, fungal, Pneumocystis) |
| HBV reactivation | Loss of immune surveillance over occult HBV → viral replication resumes | |
| Ophthalmic | Posterior subcapsular cataracts | Steroid-induced oxidative damage to lens proteins |
| Glaucoma | Increased aqueous humour resistance to outflow | |
| Dermatological | Skin thinning, striae, easy bruising, acne | Inhibition of collagen synthesis + dermal atrophy |
| Psychiatric | Insomnia, mood disturbance, psychosis | Effect on neurotransmitters (serotonin, GABA, dopamine) |
| Cardiovascular | Hypertension | Mineralocorticoid activity → sodium and water retention |
| GI | Peptic ulceration | Reduced prostaglandin synthesis → impaired gastric mucosal protection |
| Endocrine | Adrenal suppression | Exogenous steroids suppress HPA axis → adrenal atrophy; risk of adrenal crisis if steroids withdrawn abruptly |
| Growth | Growth retardation (in children) | Suppression of GH/IGF-1 axis |
| Complication | Mechanism | Monitoring |
|---|---|---|
| Myelosuppression (leukopenia, neutropenia, thrombocytopenia) | TPMT or NUDT15 deficiency → accumulation of 6-TGN → DNA damage in rapidly dividing haematopoietic cells [7] | CBC regularly (initially every 1–2 weeks, then monthly) |
| Hepatotoxicity | Cholestatic hepatitis and veno-occlusive disease — paradoxical liver injury from the drug meant to treat liver disease [5] | LFT monitoring |
| Pancreatitis | Idiosyncratic reaction (~3–5%); usually occurs within first few weeks of therapy | Clinical vigilance; amylase/lipase if symptoms |
| GI intolerance | Nausea, vomiting, abdominal pain — direct mucosal irritation | Dose reduction or switch to 6-MP or MMF |
| Increased infection risk | Immunosuppression → bacterial, viral, fungal infections | Clinical vigilance |
| Skin rash | Hypersensitivity reaction | May require drug cessation |
| Long-term lymphoma risk | Chronic immunosuppression + purine analogue mutagenesis → small increased risk of lymphoproliferative disorders | Long-term surveillance |
| Drug interaction with allopurinol/febuxostat | XO inhibition blocks 6-MP degradation → toxic accumulation [19] | Absolute contraindication to co-administer without dose reduction (reduce AZA dose by 75% if allopurinol must be used) |
| Complication | Notes |
|---|---|
| GI intolerance (diarrhoea, nausea, abdominal pain) | Most common side effect |
| Myelosuppression | Less than azathioprine in most patients |
| Teratogenicity | Absolutely contraindicated in pregnancy — causes ear, facial, limb, cardiac, and oesophageal malformations. Must use effective contraception. |
| Increased infection risk | Similar to other immunosuppressants |
For patients with decompensated AIH cirrhosis who undergo liver transplantation:
| Complication | Details |
|---|---|
| Recurrence of AIH | ~22% recurrence rate [5]; managed by step-up of immunosuppression |
| De novo AIH in graft | Can occur even in patients transplanted for non-AIH indications |
| Rejection | Standard transplant complication; managed with immunosuppression |
| Chronic immunosuppression-related complications | Infections, renal impairment (calcineurin inhibitor nephrotoxicity), malignancy (post-transplant lymphoproliferative disorder, skin cancers), metabolic syndrome |
| Surgical complications | Hepatic artery thrombosis, biliary strictures, wound infection |
Post-transplant outcomes for AIH are generally good:
"Outcome comparable with other disease necessitating transplantation. Survival: 5-year 80–90%, 10-year ~75%" [5]
Because AIH is part of a broader autoimmune diathesis, patients may develop complications from associated autoimmune conditions:
| Associated Condition | Complication |
|---|---|
| Autoimmune thyroiditis / Graves' disease | Hypothyroidism or thyrotoxicosis with associated metabolic consequences |
| Type 1 diabetes mellitus | Diabetic complications (further complicated by steroid-induced hyperglycaemia) |
| Ulcerative colitis | Colonic complications (strictures, toxic megacolon, colorectal cancer risk) |
| Sjögren's syndrome | Sicca symptoms, dental caries, parotid enlargement |
| Immune thrombocytopenia | Bleeding diathesis (compounded by cirrhosis-related coagulopathy) |
| Coeliac disease | Malabsorption (worsened by fat-soluble vitamin deficiency in cholestatic overlap) |
High Yield Summary: Complications of AIH
Disease-related complications:
- Cirrhosis is the major complication — 45–82% depending on AIH type. Untreated AIH has 50% mortality at 3–5 years.
- Cirrhosis complications: variceal bleeding, ascites, SBP, hepatic encephalopathy, hepatorenal syndrome, coagulopathy, infections.
- HCC is rare in AIH (unlike HBV/HCV) — but surveillance is still indicated once cirrhosis is established.
- Relapse occurs in 70–80% of patients after treatment withdrawal.
- Acute liver failure in ~25% presenting acutely.
Treatment-related complications:
- Steroids: osteoporosis, DM, HTN, Cushing's, cataracts, infections, HBV reactivation, adrenal suppression.
- Azathioprine: myelosuppression (check TPMT/NUDT15), pancreatitis, hepatotoxicity, drug interaction with allopurinol.
- MMF: teratogenicity (absolute contraindication in pregnancy), GI intolerance.
- Post-transplant: recurrence (~22%), rejection, chronic immunosuppression complications.
Extrahepatic: associated autoimmune diseases (thyroid, T1DM, UC, Sjögren's, ITP) contribute additional morbidity.
Key take-away: The complications of AIH are largely preventable with early diagnosis and appropriate immunosuppression. The treatment itself carries its own burden, requiring lifelong monitoring.
Active Recall - Complications of Autoimmune Hepatitis
References
[1] Lecture slides: Teaching Clinic - Non-viral chronic liver diseases (Prof. Yuen Man Fung) 2.pdf (p.7, p.9) [2] Senior notes: Maksim Medicine Notes.pdf (p.150, Autoimmune hepatitis section) [3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p.733, p.735, AIH complications and prognosis) [4] Senior notes: Block A - Gastrointestinal Data Interpretation.pdf (p.4, compensated vs decompensated cirrhosis) [5] Senior notes: Ryan Ho GI.pdf (p.280–282, AIH treatment goals, relapse, transplant outcomes) [7] Senior notes: Block A - Patients with non-viral chronic liver diseases.pdf (p.1–2) [15] Senior notes: Block A - A jaundiced and incoherent patient_ liver failure.pdf (p.12–13, complications of liver failure) [19] Senior notes: Block A - Chronic diarrhoea_ irritable bowel syndrome and inflammatory bowel disease.pdf (p.45, azathioprine pharmacology) [20] Senior notes: Ryan Ho GI.pdf (p.315, management principles for cirrhosis) [21] Senior notes: Block A - Abdominal distension_ ascites and cirrhosis.pdf (p.23) [22] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p.476, HCC aetiology)
High Yield Summary
Definition: Immune-mediated chronic hepatitis of unknown aetiology, characterised by autoantibodies, ↑IgG, and interface hepatitis on biopsy.
Epidemiology: Female predominance (F:M ≈ 4:1); bimodal age distribution (young adults and peri-menopausal); Type 1 accounts for > 95% of cases in HK.
Pathophysiology: Genetic susceptibility (HLA-DR3/DR4) + environmental trigger → loss of immune tolerance to hepatocyte antigens → CD4/CD8 T-cell-mediated hepatocyte destruction + polyclonal B-cell activation (↑IgG, autoantibodies).
Classification: Type 1 (ANA/ASMA), Type 2 (anti-LKM1), Type 3 (anti-SLA/LP — most specific).
Clinical Features:
- Variable: asymptomatic → chronic hepatitis → acute hepatitis → fulminant liver failure.
- Key symptoms: fatigue, jaundice, arthralgia (small joints), abdominal discomfort, anorexia.
- Key signs: hepatomegaly, jaundice, signs of chronic liver disease if cirrhosis present, signs of associated autoimmune diseases.
- Lab hallmarks: ↑ALT/AST (hepatitic pattern), ↑IgG (normal IgM/IgA), positive autoantibodies.
HCC risk is rare in AIH (unlike HBV/HCV cirrhosis).
Diagnosis is partly by exclusion — must rule out viral hepatitis, DILI, alcohol, Wilson's, metabolic causes.
Key exam scenarios: Young woman with acute hepatitis and negative viral markers; cryptogenic cirrhosis in an elderly patient; patient with multiple autoimmune diseases found to have elevated transaminases.
High Yield Summary: Differential Diagnosis of AIH
-
The differential depends on the presentation — acute hepatitis vs chronic hepatitis vs cholestatic vs fulminant vs cryptogenic cirrhosis.
-
Must-exclude differentials: Viral hepatitis (HBV, HCV, HAV, HEV), DILI (including herbal/TCM), alcoholic liver disease, Wilson's disease, haemochromatosis, α1-antitrypsin deficiency, PBC, PSC.
-
Key differentiating features of AIH: Negative viral markers, no drug/alcohol history, elevated IgG (not IgM or IgA), positive autoantibodies (ANA/ASMA/anti-LKM1/anti-SLA), interface hepatitis with plasma cells on biopsy.
-
Immunoglobulin pattern: ↑IgG = AIH; ↑IgM = PBC; ↑IgA = Alcoholic hepatitis.
-
AST:ALT ratio: ALT > AST in most primary liver diseases including AIH; AST > ALT in alcoholic hepatitis (> 2:1), HCC, CHF, ischaemic hepatitis.
-
Wilson's in fulminant liver failure: Coombs-negative haemolytic anaemia + low ceruloplasmin is the clue.
-
HK context: Always exclude HBV first; dual liver disease is common; ask about TCM/herbal use; MASLD is increasingly prevalent.
High Yield Summary: Diagnosis of AIH
No single test is diagnostic — AIH diagnosis requires a composite approach:
- Hepatitic LFT pattern (↑ALT/AST, normal-mild ALP)
- Negative viral markers (HBsAg, anti-HCV, IgM anti-HAV, IgM anti-HEV)
- Elevated IgG (with normal IgM and IgA)
- Positive autoantibodies (ANA/ASMA for Type 1; anti-LKM1 for Type 2; anti-SLA/LP most specific)
- Liver biopsy: interface hepatitis + plasma cell-rich infiltrate = hallmark
- Exclusion of drugs/alcohol/metabolic causes (Wilson's, haemochromatosis, α1-AT deficiency)
Simplified Scoring: ≥ 7 = definite, ≥ 6 = probable (4 variables: autoantibodies, IgG, histology, viral exclusion)
Immunoglobulin pattern: ↑IgG = AIH, ↑IgM = PBC, ↑IgA = Alcoholic hepatitis
Histology hallmarks: Interface hepatitis, lymphoplasmacytic infiltrate (especially plasma cells), rosettes, emperipolesis
Response to corticosteroids further supports the diagnosis
High Yield Summary: Management of AIH
Indications for treatment (AASLD): ALT > 10× ULN; ALT > 5× ULN + γ-globulin ≥ 2× ULN; bridging/multiacinar necrosis; symptomatic patients. Can also treat milder disease to prevent progression.
Pre-treatment checks: TPMT, NUDT15 (especially in Asian populations), HBV serology (start antiviral prophylaxis if HBsAg+ or anti-HBc+), TB screening, xanthine oxidase inhibitor co-administration.
First-line: Predniso(lo)ne + azathioprine. Start steroid, taper over 4–12 weeks, maintain on azathioprine for years/decades.
Monotherapy indications: Cytopenia, TPMT deficiency, malignancy, pregnancy.
Monitoring: ALT, IgG, γ-globulin every 3–6 months. Autoantibody titres do NOT correlate with disease activity.
Second-line: Mycophenolate mofetil (increasingly used, may replace AZA). Tacrolimus, ciclosporin for refractory cases.
Relapse rate: 70–80% after treatment withdrawal → most patients need lifelong therapy.
Budesonide: Only in non-cirrhotic patients (first-pass metabolism lost with cirrhotic shunting).
HBV prophylaxis: Mandatory in HK — check before any immunosuppression.
High Yield Summary: Complications of AIH
Disease-related complications:
- Cirrhosis is the major complication — 45–82% depending on AIH type. Untreated AIH has 50% mortality at 3–5 years.
- Cirrhosis complications: variceal bleeding, ascites, SBP, hepatic encephalopathy, hepatorenal syndrome, coagulopathy, infections.
- HCC is rare in AIH (unlike HBV/HCV) — but surveillance is still indicated once cirrhosis is established.
- Relapse occurs in 70–80% of patients after treatment withdrawal.
- Acute liver failure in ~25% presenting acutely.
Treatment-related complications:
- Steroids: osteoporosis, DM, HTN, Cushing's, cataracts, infections, HBV reactivation, adrenal suppression.
- Azathioprine: myelosuppression (check TPMT/NUDT15), pancreatitis, hepatotoxicity, drug interaction with allopurinol.
- MMF: teratogenicity (absolute contraindication in pregnancy), GI intolerance.
- Post-transplant: recurrence (~22%), rejection, chronic immunosuppression complications.
Extrahepatic: associated autoimmune diseases (thyroid, T1DM, UC, Sjögren's, ITP) contribute additional morbidity.
Key take-away: The complications of AIH are largely preventable with early diagnosis and appropriate immunosuppression. The treatment itself carries its own burden, requiring lifelong monitoring.