Membranoproliferative Glomerulonephritis
Membranoproliferative glomerulonephritis is a pattern of glomerular injury with basement membrane thickening and mesangial hypercellularity, often presenting with mixed nephrotic and nephritic features.
Membranoproliferative Glomerulonephritis (MPGN)
Membranoproliferative glomerulonephritis (MPGN) — let's break down the name:
- "Membrano-" = relating to the glomerular basement membrane (GBM)
- "Proliferative" = increased cellularity (mesangial cell proliferation + inflammatory cell infiltration)
- "Glomerulonephritis" = inflammation of the glomeruli ("glomerulo" = glomerulus, "nephritis" = kidney inflammation)
So the name itself tells you exactly what you see under the microscope: thickening of the glomerular basement membrane combined with proliferation of mesangial cells, producing a characteristic lobulated appearance of the glomerulus.
MPGN is a pattern of glomerular injury on light microscopy, NOT a single disease [1][2]. This is a critical conceptual point. MPGN is defined by its histological pattern — mesangial hypercellularity, GBM thickening/duplication ("double contour" or "tram-track" appearance), and lobular accentuation of the glomerular tuft. Multiple different diseases can produce this pattern.
High Yield: MPGN is classified as a proliferative primary glomerulonephritis. It can present with nephrotic syndrome (occasionally), nephritic syndrome, or a mixed nephritic-nephrotic picture — it is one of the few glomerular diseases that classically overlaps both syndromes [1][2][3].
MPGN is classified under proliferative glomerulonephritis alongside IgA nephropathy and crescentic GN in the primary category, and alongside lupus nephritis, post-streptococcal GN, and HBV/HCV-related MPGN in the secondary category [1][2].
2. Epidemiology
- MPGN accounts for approximately 5–10% of all primary glomerulonephritides in adults and a smaller proportion in children
- It is relatively uncommon compared to IgA nephropathy (the most common primary GN worldwide) and membranous nephropathy
- Bimodal age distribution: can present in children/adolescents (historically more common in paediatrics, especially MPGN Type II/C3 glomerulopathy) and in middle-aged adults (often secondary causes)
- No strong sex predilection overall, though some series suggest slight male predominance
- In Hong Kong, IgA nephropathy is by far the most common primary GN — MPGN is relatively rare
- HBV- and HCV-related MPGN are important secondary causes in Hong Kong given the relatively high prevalence of chronic hepatitis B (~8% of the population are HBsAg carriers historically) and the presence of hepatitis C [1][2]
- HCV extrahepatic manifestation: membranoproliferative glomerulonephritis (screening recommended) [4]
- Lupus nephritis (another cause of MPGN pattern) is relatively common in young Chinese women
- The incidence of primary (idiopathic) MPGN has declined over the past few decades in developed countries, partly due to:
- Better recognition and treatment of underlying infections (HCV, HBV)
- Reclassification: many previously "idiopathic" cases are now recognized as complement-mediated (C3 glomerulopathy) or immune complex-mediated with identifiable causes
- The modern reclassification system (2012 onwards) has shifted the paradigm from a morphology-based to a pathogenesis-based approach
3. Anatomy and Function Review
To understand MPGN you must understand glomerular microanatomy:
- Fenestrated endothelium — the innermost layer facing the capillary lumen; has pores (~70–100 nm) that allow passage of plasma but block blood cells
- Glomerular basement membrane (GBM) — the middle acellular layer; a specialized extracellular matrix composed of type IV collagen, laminin, proteoglycans (heparan sulfate providing charge selectivity), and nidogen. Acts as both a size and charge barrier
- Podocytes (visceral epithelial cells) — the outermost layer; have interdigitating foot processes connected by slit diaphragms (nephrin, podocin proteins). This is the final size-selective barrier
- Mesangial cells sit between and support the capillary loops within the glomerulus
- They produce mesangial matrix (similar to basement membrane material)
- Functions: structural support, regulation of glomerular blood flow (contractile), phagocytosis and clearance of macromolecules/immune complexes from the GBM
- In MPGN, mesangial cells proliferate and extend into the subendothelial space (mesangial interposition), which is the key pathological event leading to GBM duplication
- The alternative pathway of complement is normally in a state of low-level continuous activation ("tick-over" of C3)
- Regulatory proteins (Factor H, Factor I, Factor B, MCP/CD46) keep this in check
- If regulation fails → uncontrolled complement activation on the GBM → C3 deposition → inflammation → MPGN pattern
4. Etiology
The traditional classification (Type I, II, III based on electron microscopy location of deposits) has been superseded by a pathogenesis-based classification since approximately 2012–2013 (Sethi & Fervenza, JASN 2012). This is because the EM-based classification didn't correlate well with clinical outcomes or guide treatment.
The modern approach divides MPGN into two major categories based on immunofluorescence (IF) findings:
A. Immune Complex-Mediated MPGN (IF: Ig + Complement)
These are driven by chronic antigenemia → persistent immune complex formation → deposition in the glomerulus → complement activation via the classical pathway → inflammation and MPGN pattern.
| Infection | Mechanism | HK Relevance |
|---|---|---|
| Hepatitis C virus (HCV) | Chronic HCV → mixed cryoglobulinaemia (type II) → cryoglobulins deposit in glomeruli → complement activation. HCV extrahepatic manifestation: MPGN (screening recommended) [4] | Genotypes 1 and 6 commonest in HK [4] |
| Hepatitis B virus (HBV) | HBsAg-HBsAb immune complexes deposit in glomeruli | HBV/HCV-related MPGN is listed as a secondary proliferative GN [1][2] |
| Infective endocarditis | Chronic bacteraemia → immune complex formation | Universal |
| Shunt nephritis | Infected ventriculoatrial shunts → chronic antigenemia | Rare but classic |
| Other chronic infections | Malaria, schistosomiasis, mycobacterial | Less relevant in HK |
| Disease | Mechanism |
|---|---|
| Systemic lupus erythematosus (SLE) | Anti-dsDNA and other antibodies → immune complex deposition. Lupus nephritis can produce MPGN pattern (especially Class III/IV) [2][5] |
| Cryoglobulinaemia | Types I, II, III — proteins precipitate at cold temperatures, deposit in glomeruli |
| Sjögren syndrome | Immune complex-mediated |
| Condition | Mechanism |
|---|---|
| Monoclonal gammopathy of renal significance (MGRS) | Monoclonal Ig (from a small B-cell clone) deposits in glomeruli. The clone is too small to qualify as myeloma/lymphoma but big enough to cause kidney damage |
| Multiple myeloma | Monoclonal light/heavy chains deposit. An old man with bone pain and anaemia — myeloma must be excluded in older patients with MPGN [6] |
| Waldenström macroglobulinaemia | IgM paraprotein deposition |
| Chronic lymphocytic leukaemia (CLL) | Paraprotein-mediated |
High Yield — HKUMed Exam Point: In an older patient (> 40 years) presenting with MPGN pattern on biopsy, you must screen for monoclonal gammopathy (serum and urine protein electrophoresis, serum free light chains, immunofixation). This is MGRS until proven otherwise [6].
- When all secondary causes above have been excluded
- Increasingly rare as diagnostic techniques improve
IF shows dominant C3 deposition with absent or minimal immunoglobulin staining. This defines the entity of C3 glomerulopathy (C3G), which is subdivided by EM into:
| Subtype | EM Appearance | Pathogenesis |
|---|---|---|
| C3 Glomerulonephritis (C3GN) | Mesangial, subendothelial, and/or subepithelial electron-dense deposits (varied locations) | Dysregulation of the alternative complement pathway |
| Dense Deposit Disease (DDD) (formerly MPGN Type II) | Characteristic highly electron-dense, ribbon-like intramembranous deposits within the GBM (the deposits are so electron-dense they look like a dark stripe running through the GBM) | Uncontrolled alternative pathway activation — often due to C3 nephritic factor (C3NeF), an autoantibody that stabilizes C3 convertase, preventing its normal breakdown |
Why does complement dysregulation cause MPGN?
- Uncontrolled C3 activation → C3b deposition on GBM and mesangium → recruitment of inflammatory cells → mesangial proliferation → GBM damage → characteristic MPGN pattern
- Causes of alternative pathway dysregulation:
- C3 nephritic factor (C3NeF): autoantibody against C3bBb convertase → stabilizes it → persistent C3 cleavage → low serum C3
- Genetic mutations: Factor H, Factor I, Factor B, C3, MCP/CD46 — loss-of-function in regulatory proteins or gain-of-function in activation proteins
- Anti-Factor H antibodies: acquired inhibition of complement regulation
Complement Connection
Think of it this way: if the "brakes" on the alternative complement pathway are broken (loss of Factor H, Factor I) or the "accelerator" is stuck (C3NeF stabilizing the convertase), complement activation runs unchecked → C3 fragments deposit on the GBM → inflammation → MPGN pattern. This is analogous to how atypical HUS is also a disease of complement dysregulation, but affecting the endothelium of small vessels rather than the glomerular mesangium.
5. Pathophysiology — Linking Etiology to Histology to Clinical Features
Step 1: Initiating Event
- Immune complexes deposit in the subendothelial space and mesangium (immune complex-mediated)
- OR complement fragments (C3b, C3c, C3d) deposit along the GBM (complement-mediated)
Step 2: Mesangial Response
- Mesangial cells are activated → proliferate (hence "proliferative")
- Activated mesangial cells interpose (extend) themselves between the endothelium and the GBM → this creates a new layer of basement membrane-like material on the inner (subendothelial) side
- This "sandwich" of original GBM + new mesangial-derived matrix = "double contour" or "tram-track" appearance on silver stain or PAS stain under light microscopy
Step 3: Inflammatory Amplification
- Complement activation (classical or alternative pathway depending on etiology) → C5a generation → neutrophil and monocyte recruitment
- Release of proteases, reactive oxygen species → further GBM damage
- Matrix expansion → lobular accentuation of glomerular tuft
Step 4: Consequences on the Filtration Barrier
- GBM thickening + duplication → disruption of size and charge selectivity → proteinuria (can reach nephrotic range)
- Endothelial/mesangial proliferation + inflammation → reduced capillary lumen → reduced GFR (nephritic features: oliguria, rising creatinine)
- Inflammatory breach of GBM → red blood cells leak through → haematuria (with dysmorphic RBCs and RBC casts)
- Reduced GFR + sodium/water retention → oedema and hypertension
| Feature | Mechanism |
|---|---|
| Heavy proteinuria / nephrotic syndrome | GBM structural disruption + podocyte injury → loss of size/charge selectivity |
| Haematuria | Inflammatory disruption of GBM integrity → RBC leakage |
| Hypertension | Reduced GFR → sodium/water retention; also RAAS activation |
| Renal impairment | Reduced capillary lumen from mesangial proliferation; crescent formation if severe |
| Low complement | Consumption via classical (immune complex) or alternative (C3G) pathway |
MPGN characteristically shows: proteinuria (++), nephrotic (++), nephritic (+), haematuria (+), ARF (+), CRF (+) — it is the quintessential "mixed" glomerulonephritis [3].
Persistently low C3 > 8 weeks raises the possibility of lupus nephritis or membranoproliferative glomerulonephritis (complement-mediated MPGN) [7].
| Etiology | C3 | C4 | Pathway Activated |
|---|---|---|---|
| Post-streptococcal GN | ↓ (transient, normalizes by 8 weeks) | Normal | Alternative |
| MPGN (immune complex-mediated, e.g. HCV/cryoglobulinaemia) | ↓ | ↓ | Classical |
| MPGN (C3 glomerulopathy / DDD) | ↓↓ (often profoundly low) | Normal | Alternative |
| Lupus nephritis | ↓ | ↓ | Classical |
Clinical Pearl — Persistently Low C3
A common exam trap: PSGN causes low C3 that normalizes within 6–8 weeks. If C3 remains low beyond 8 weeks, you must consider MPGN or lupus nephritis. Do NOT label it as "persistent PSGN" — re-investigate! [7]
6. Classification
| Type | Deposit Location (EM) | Modern Equivalent |
|---|---|---|
| MPGN Type I | Subendothelial + mesangial deposits | Immune complex-mediated MPGN or C3GN |
| MPGN Type II | Intramembranous dense deposits | Dense Deposit Disease (C3G) |
| MPGN Type III | Subendothelial + subepithelial deposits | Immune complex-mediated MPGN or C3GN |
| Category | IF Pattern | Subtypes | Key Causes |
|---|---|---|---|
| Immune complex-mediated MPGN | Ig + C3 | — | HCV, HBV, SLE, cryoglobulinaemia, MGRS |
| Complement-mediated (C3 Glomerulopathy) | C3 dominant, Ig-negative/trace | C3GN, DDD | C3NeF, Factor H/I mutations, anti-Factor H Ab |
7. Clinical Features
| Symptom | Pathophysiological Basis |
|---|---|
| Haematuria (gross or microscopic — "tea-coloured" or "cola-coloured" urine) | Inflammatory breach of the GBM → RBCs leak into Bowman's space → dysmorphic RBCs in urine. May be gross (especially during intercurrent infections which boost immune complex formation) |
| Frothy urine | Heavy proteinuria → protein in urine creates foam (proteins reduce surface tension of urine) |
| Peripheral oedema (face, periorbital in mornings; leg swelling later in day) | Two mechanisms: (1) nephrotic: hypoalbuminaemia → decreased oncotic pressure → fluid shifts to interstitium; (2) nephritic: sodium/water retention from reduced GFR |
| Weight gain | Fluid retention (oedema) |
| Oliguria / reduced urine output | Reduced GFR from mesangial proliferation occluding capillary lumens + inflammatory swelling |
| Fatigue / malaise | Uraemia from declining renal function; anaemia from chronic disease |
| Headache | Hypertension secondary to sodium/water retention |
| Nausea / poor appetite | Uraemia (accumulation of nitrogenous waste) |
| Dyspnoea | Fluid overload → pulmonary oedema (if severe nephrotic/nephritic syndrome) |
Symptoms related to underlying cause:
| Underlying Cause | Associated Symptoms |
|---|---|
| HCV | Fatigue, arthralgia, Raynaud phenomenon, purpura (cryoglobulinaemia), skin manifestations (porphyria cutanea tarda, lichen planus) [4] |
| HBV | May be asymptomatic carrier; jaundice if active hepatitis |
| SLE | Facial rash (malar/butterfly rash), photosensitivity, oral ulcers, hair loss, arthralgia of small joints, Raynaud phenomenon, serositis (pleurisy, pericarditis) [5] |
| Cryoglobulinaemia | Purpura, arthralgia, peripheral neuropathy, Raynaud phenomenon |
| Monoclonal gammopathy / Myeloma | Bone pain, anaemia, hypercalcaemia, weight loss, recurrent infections [6] |
| Infective endocarditis | Fever, new murmur, splinter haemorrhages, Janeway lesions, Osler nodes |
| Sign | Pathophysiological Basis |
|---|---|
| Hypertension | Reduced GFR → activation of RAAS (renin-angiotensin-aldosterone system) → sodium/water retention → volume expansion → elevated BP. Hypertension is a hallmark of nephritic syndrome |
| Peripheral oedema (pitting) | Nephrotic: ↓albumin → ↓intravascular oncotic pressure → fluid extravasation. Nephritic: ↓GFR → Na+/H₂O retention → volume expansion |
| Periorbital oedema (especially morning) | Loose periorbital connective tissue allows fluid accumulation early; gravity-dependent oedema (legs) develops later in the day |
| Ascites / pleural effusion (if severe nephrotic syndrome) | Profound hypoalbuminaemia → third-space fluid collection |
| Pallor | Anaemia of chronic kidney disease (reduced erythropoietin) or haemolytic anaemia if associated with TMA |
| Xanthelasma / tendon xanthomata (rare, chronic nephrotic syndrome) | Hyperlipidaemia secondary to nephrotic syndrome (liver upregulates lipoprotein synthesis in response to hypoalbuminaemia) |
| Lipodystrophy (partial) | Specifically associated with C3 glomerulopathy / DDD — loss of subcutaneous fat (especially upper body) due to complement-mediated adipocyte lysis (C3NeF activates complement in adipose tissue) |
| Signs of underlying disease | Malar rash (SLE), purpura (cryoglobulinaemia/vasculitis), hepatomegaly/stigmata of chronic liver disease (HBV/HCV), splenomegaly (lymphoproliferative disease) |
| Finding | Significance |
|---|---|
| Dysmorphic RBCs | Glomerular origin haematuria — RBCs are deformed as they squeeze through the damaged GBM |
| RBC casts | Pathognomonic of glomerulonephritis — RBCs trapped in Tamm-Horsfall protein matrix in the tubules |
| Proteinuria (subnephrotic to nephrotic range) | GBM damage → loss of size/charge selectivity |
| Lipiduria (oval fat bodies, fatty casts) | In nephrotic-range proteinuria; filtered lipoproteins and free cholesterol in urine |
MPGN — The Great Mimicker
MPGN can present as virtually any glomerular syndrome: asymptomatic proteinuria/haematuria, acute nephritic syndrome, nephrotic syndrome, mixed nephritic-nephrotic, RPGN (if crescents develop), or slowly progressive CKD. The clinical presentation depends on the severity of histological changes and the underlying cause. Always look for the underlying driver — especially HCV, HBV, SLE, cryoglobulinaemia, and monoclonal gammopathy.
From the nephrology data interpretation table [3]:
| Feature | MPGN Rating |
|---|---|
| Proteinuria | ++ |
| Nephrotic | ++ |
| Nephritic | + |
| Haematuria | + |
| ARF | + |
| CRF | + |
This highlights that MPGN is a "jack of all trades" — moderate across all clinical presentations. Compare this to MCD (pure nephrotic, no haematuria) or PSGN (pure nephritic, minimal proteinuria).
9. Histopathological Features (Essential for Understanding)
Since renal biopsy is still essential for definitive diagnosis of MPGN [8], understanding the histology is key:
- Mesangial hypercellularity — increased number of mesangial cells (> 3 per mesangial area)
- GBM thickening and splitting — the "double contour" / "tram-track" appearance (best seen on PAS or silver stain) caused by mesangial interposition between the endothelium and GBM with deposition of new basement membrane material
- Lobular accentuation of the glomerular tuft — exaggeration of the normal lobular architecture due to mesangial expansion
- Endocapillary proliferation — increased cellularity within capillary lumens
- Possible crescent formation if disease is severe/rapidly progressive
- Immune complex-mediated MPGN: granular deposits of IgG, IgM, C3, C1q along capillary walls and mesangium
- C3 Glomerulopathy: dominant C3 staining with absent or scanty immunoglobulin (by definition, C3 staining intensity must be ≥ 2 orders of magnitude greater than any Ig staining)
- Immune complex MPGN (old Type I/III): electron-dense deposits in subendothelial (Type I) ± subepithelial (Type III) locations
- DDD (old Type II): dense, ribbon-like intramembranous deposits within the lamina densa of the GBM — highly characteristic and virtually diagnostic
- C3GN: deposits in varied locations (mesangial, subendothelial, subepithelial, intramembranous) but NOT the characteristic "dense deposit" pattern of DDD
| Term | Definition |
|---|---|
| Focal | < 50% of glomeruli involved |
| Diffuse | > 50% of glomeruli involved |
| Segmental | < 50% of area within a single glomerulus involved |
| Global | > 50% of area within a single glomerulus involved |
| Proliferative | Increased cellularity from proliferation of native glomerular cells or WBC infiltration |
| Membrane thickening | Thickening of GBM per se, or more often due to protein (esp Ab or immune complex) deposition either side of or within the GBM |
| Crescent formation | Cellular crescents from proliferating epithelial cells + infiltrating leukocytes — pathognomonic of RPGN |
| Sclerosis | Replacement of glomerular tissue by hyaline fibrous scar tissue |
High Yield Summary
Definition: MPGN is a histological pattern (not a single disease) defined by mesangial proliferation + GBM thickening/duplication ("tram-track") on light microscopy.
Modern Classification (pathogenesis-based):
- Immune complex-mediated MPGN (IF: Ig + C3) — caused by HCV, HBV, SLE, cryoglobulinaemia, MGRS/myeloma, infective endocarditis
- Complement-mediated / C3 Glomerulopathy (IF: C3 dominant, Ig-negative) — subdivided into C3GN and DDD; caused by alternative complement pathway dysregulation (C3NeF, Factor H/I mutations)
Clinical Presentation: Mixed nephrotic-nephritic picture. Proteinuria (++), haematuria (+), nephrotic (++), nephritic (+), ARF (+), CRF (+). Can present as any glomerular syndrome.
Key Diagnostic Clue: Persistently low C3 > 8 weeks (unlike PSGN which normalizes by 8 weeks) — think MPGN or lupus nephritis.
Complement Pattern:
- IC-MPGN (classical pathway): ↓C3, ↓C4
- C3G (alternative pathway): ↓↓C3, normal C4
Must-Exclude Causes in HK: HCV (with cryoglobulins), HBV, SLE, monoclonal gammopathy (especially in older patients).
Histology Hallmarks: Tram-track GBM (LM), lobular accentuation (LM), IF pattern determines subtype, DDD has intramembranous dense deposits (EM).
Renal biopsy is essential for definitive diagnosis and to guide treatment.
Active Recall - Membranoproliferative Glomerulonephritis
[1] Lecture slides: Glomerular diseases.pdf (p10 — Major causes of nephrotic syndrome; classification table) [2] Senior notes: Ryan Ho Urogenital.pdf (p54 — Classification of GN by cellularity, proliferative vs non-proliferative) [3] Senior notes: Block A – Nephrology Data Interpretation.pdf (p17 — Clinical presentation table of GN) [4] Senior notes: Ryan Ho GI.pdf (p232 — HCV extrahepatic manifestations including MPGN) [5] Lecture slides: GC 046. Facial rash and painful fingers_SLE.pdf [6] Lecture slides: GC 030. An old man with bone pain and anaemia.pdf [7] Senior notes: Block A - Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p19 — Persistently low C3) [8] Senior notes: Block A - Nephrotology Teaching Clinic RTD.pdf (p4 — Renal biopsy for definitive diagnosis)
Differential Diagnosis of MPGN
Before diving into the list, let's clarify what we are actually differentiating. When a patient presents with features suggestive of MPGN — typically a mixed nephrotic-nephritic picture (proteinuria, haematuria, hypertension, oedema, impaired renal function, and low complement) — you need to think at two levels:
- Level 1 — What other glomerular diseases can mimic this clinical presentation? (i.e., DDx of the clinical syndrome)
- Level 2 — Once biopsy confirms an MPGN pattern, what is the underlying cause driving it? (i.e., DDx of the MPGN histological pattern itself)
Both are essential for exams and for clinical practice. Let's address both systematically.
The presentation that should make you think of MPGN is: proteinuria (often nephrotic range), active urine sediment (dysmorphic RBCs, RBC casts), hypertension, renal impairment, and hypocomplementaemia. The key differentials overlap because several glomerular diseases share these features.
Approach by Complement Level
This is the single most powerful discriminator at the bedside before biopsy:
Hypocomplementaemia is seen in lupus nephritis, post-infectious glomerulonephritis, membranoproliferative glomerulonephritis, and mixed cryoglobulinaemia [9][10].
Complement level is normal in patients with primary (idiopathic) nephrotic syndrome [10].
High Yield — GC Exam Point
Persistently low C3 > 8 weeks should raise suspicion of lupus nephritis or MPGN [7][11]. PSGN causes transient low C3 that normalizes within 6–8 weeks. If it doesn't normalize — rethink the diagnosis.
↓ C3 level in MPGN, post-infectious GN including PSGN and infective endocarditis. ↓ C3 and C4 level in lupus nephritis [10].
The Major Differentials — Explained From First Principles
Why it's in the DDx: PSGN is the prototypical acute nephritic syndrome — haematuria, oedema, hypertension, oliguria, with low C3. The acute presentation of MPGN may be indistinguishable from PSGN, but MPGN usually persists beyond 4–6 weeks with further increase in serum creatinine [11].
| Feature | PSGN | MPGN |
|---|---|---|
| Latent period | 1–3 weeks after pharyngitis, 3–6 weeks after skin infection [11] | No characteristic latent period |
| Age | Most common in children aged 5–12 [12] | Any age; bimodal (children for C3G, adults for IC-MPGN) |
| C3 | Low, normalizes by 4–8 weeks [7][11] | Persistently low |
| C4 | Normal (alternative pathway) | Low if classical pathway (IC-MPGN), normal if alternative (C3G) |
| Clinical course | Self-limiting; diuresis in 1–2 weeks, RFT normalizes in 4 weeks [11] | Progressive; does NOT spontaneously resolve |
| ASO titre | May be raised [7] | Not elevated |
| Renal biopsy | Usually NOT done [11] | Required for definitive diagnosis |
| EM | Subepithelial humps ("starry sky") [13] | Subendothelial deposits (Type I) or intramembranous dense deposits (DDD) |
The discriminating principle: Time. PSGN resolves. MPGN does not. If clinical features or low C3 persist beyond 6–8 weeks, suspect MPGN.
Why it's in the DDx: Lupus nephritis is classified as a secondary proliferative GN [2] and can produce an MPGN-like histological pattern (especially Class III/IV diffuse proliferative lupus nephritis). It also causes hypocomplementaemia. In Hong Kong, SLE is relatively common in young Chinese women.
| Feature | Lupus Nephritis | MPGN |
|---|---|---|
| Demographics | Young women (F:M ~9:1), especially East Asian | No strong sex predilection |
| Extrarenal features | Malar rash, photosensitivity, oral ulcers, arthralgia, serositis, hair loss [5] | Usually no extrarenal features (unless secondary to SLE or HCV) |
| Complement | ↓C3 and ↓C4 (classical pathway) [10] | ↓C3 ± ↓C4 depending on mechanism |
| Autoantibodies | ANA positive, anti-dsDNA positive [9] | ANA/anti-dsDNA negative (unless MPGN is secondary to SLE) |
| IF pattern | "Full house" — IgG, IgA, IgM, C3, C1q | Granular Ig + C3 (IC-MPGN) or C3-dominant (C3G) |
The discriminating principle: Systemic features of SLE + positive ANA/anti-dsDNA + "full house" IF. If your MPGN patient has positive ANA and extrarenal features — think lupus nephritis as the underlying driver.
Lupus or MPGN?
Remember: SLE can cause an MPGN histological pattern. So the real question is — is this primary MPGN, or is this lupus nephritis presenting with an MPGN pattern? Check ANA, anti-dsDNA, and look for extrarenal SLE features.
Why it's in the DDx: IgA nephropathy is the most common primary GN globally and in Hong Kong [14]. It can present with haematuria and proteinuria, occasionally with nephrotic features. However, the clinical pattern differs.
| Feature | IgA Nephropathy | MPGN |
|---|---|---|
| Classic presentation | Recurrent synpharyngitic haematuria — gross haematuria within 1–2 days of URTI [15]. "Syn-" means simultaneous, not delayed like PSGN. | No temporal relationship to infections |
| Complement | Normal C3 and C4 — IgA nephropathy is NOT usually associated with complement consumption [11] | Low C3 ± low C4 |
| IF pattern | Dominant mesangial IgA deposits | IgG/IgM/C3 (IC-MPGN) or C3-dominant (C3G) |
| Serum IgA | Elevated in ~50% [15] | Not elevated |
| Histology | Mesangial proliferative GN (MEST criteria) | Mesangial + endocapillary proliferative + GBM duplication |
The discriminating principle: Normal complement + synpharyngitic timing + mesangial IgA on biopsy = IgA nephropathy, not MPGN.
Why it's in the DDx: Essential mixed cryoglobulinaemia (Type II) is a classic cause of immune complex-mediated MPGN. It is strongly associated with HCV [4]. The clinical presentation overlaps heavily with MPGN because cryoglobulinaemia IS one of the causes of MPGN.
| Feature | Cryoglobulinaemia | Primary MPGN |
|---|---|---|
| Triad | Purpura + arthralgia + weakness (Meltzer triad) | No classic triad |
| Complement | ↓C3, ↓↓C4 (classical pathway activation with disproportionately low C4) | Variable |
| Serum cryoglobulins | Positive cryocrit [9] | Negative |
| Associated infection | HCV (> 90% of mixed cryoglobulinaemia cases) [4] | May or may not have HCV |
| Peripheral neuropathy | Common (vasa nervorum involvement) | Not typical |
The discriminating principle: Disproportionately low C4, palpable purpura, positive cryocrit, and HCV seropositivity all point to cryoglobulinaemia.
Why it's in the DDx: ANCA vasculitis (GPA, MPA, EGPA) can cause rapidly progressive GN with haematuria and proteinuria, mimicking MPGN. However, it is a fundamentally different mechanism — pauci-immune (no or minimal immune deposits on IF) [16].
| Feature | ANCA Vasculitis | MPGN |
|---|---|---|
| ANCA | Positive (c-ANCA/PR3 for GPA; p-ANCA/MPO for MPA) [9] | Negative |
| Complement | Normal | Low |
| IF | Negative (pauci-immune) — this is the hallmark [16] | Positive (Ig ± C3) |
| Extrarenal features | Sinusitis, epistaxis, pulmonary nodules (GPA); purpura, neuropathy (MPA) | Usually none unless secondary cause |
| Histology | Crescentic GN (necrotizing) | Mesangial proliferative + GBM duplication |
The discriminating principle: Normal complement + positive ANCA + pauci-immune IF = vasculitis, not MPGN.
Why it's in the DDx: Presents with RPGN (haematuria, rapidly declining renal function) ± pulmonary haemorrhage. Can be confused with severe MPGN presenting as RPGN.
| Feature | Anti-GBM Disease | MPGN |
|---|---|---|
| Pulmonary haemorrhage | Classic (Goodpasture syndrome) — haemoptysis, dyspnoea, infiltrates on CXR [16] | Not typical |
| Anti-GBM Ab | Positive [9] | Negative |
| Complement | Normal | Low |
| IF | Linear IgG staining along GBM [16] | Granular (IC-MPGN) or C3-dominant (C3G) |
| Speed of decline | Days to weeks (RPGN) | Usually more indolent (weeks to months) |
| Treatment | Plasmapheresis (to remove circulating anti-GBM antibodies) [16] | Depends on etiology |
The discriminating principle: Linear IF staining + positive anti-GBM antibody + pulmonary-renal syndrome.
Why it's in the DDx: Both MPGN and membranous nephropathy cause nephrotic syndrome with GBM thickening. However, membranous nephropathy is non-proliferative [2] and presents with a bland sediment.
| Feature | Membranous Nephropathy | MPGN |
|---|---|---|
| Sediment | Bland (inactive) sediment — oval fat bodies, hyaline casts, few RBCs [10] | Active sediment — dysmorphic RBCs, RBC casts [15] |
| Complement | Normal | Low |
| Proliferation | No proliferation (non-proliferative GN) [2] | Proliferative |
| Anti-PLA2R | Positive in ~70% of primary cases [15] | Negative |
| EM | Subepithelial deposits ("spike and dome") [15] | Subendothelial (Type I) or intramembranous (DDD) |
The discriminating principle: Bland sediment + normal complement + non-proliferative histology = membranous. Active sediment + low complement + proliferative histology = MPGN.
Why they're in the DDx: Both cause nephrotic syndrome, which MPGN can also cause. However:
In an older patient (> 40 years), MPGN pattern on biopsy must prompt screening for monoclonal gammopathy [6]. The monoclonal immunoglobulin deposits in the glomerulus and drives the MPGN pattern. This is not really a separate differential — it is an underlying cause of immune complex-mediated MPGN — but you must think of it.
Workup for GN includes malignancy screen (e.g. tumour markers, SIEP) especially in elderly [17][18].
Once the renal biopsy shows an MPGN pattern, the IF results divide you into two camps:
The IF pattern is the key discriminator for determining the underlying cause of MPGN:
| IF Finding | Category | Differential of Underlying Cause |
|---|---|---|
| Ig + C3 (granular) | Immune complex-mediated | HBV/HCV, SLE (Class IV), Cryoglobulinaemia, MGRS/Myeloma/CLL, Malignancy (lung/breast/ovary), Infective endocarditis [13][19] |
| C3-dominant (Ig-negative) | C3 Glomerulopathy | C3GN or DDD — due to alternative complement pathway dysregulation (C3NeF, Factor H/I mutations, anti-Factor H Ab) |
This is a critical distinction because:
- Immune complex-mediated MPGN → treat the underlying cause (e.g., DAAs for HCV, immunosuppression for SLE, chemotherapy for MGRS)
- C3 Glomerulopathy → complement-directed therapies are being explored; prognosis is generally worse
High Yield: Type I MPGN: HBV/HCV, Autoimmune diseases (SLE Class IV, Cryoglobulinaemia), Malignancy (CLL/MM/Lung/Breast/Ovary). Type II and III MPGN: Idiopathic [13][19].
| Diagnosis | Complement | ANCA | Anti-GBM | ANA/dsDNA | Cryoglobulins | IF Pattern | Key Clinical Clue |
|---|---|---|---|---|---|---|---|
| MPGN (IC-mediated) | ↓C3 ± ↓C4 | − | − | − | ± | Granular Ig + C3 | Mixed nephrotic/nephritic, persistent |
| MPGN (C3G/DDD) | ↓↓C3, N C4 | − | − | − | − | C3-dominant | Young patient, ± lipodystrophy |
| PSGN | ↓C3 (transient) | − | − | − | − | Granular IgG/C3 | Post-strep, self-resolving ≤ 4–8 wk |
| Lupus nephritis | ↓C3, ↓C4 | − | − | + | ± | "Full house" | Young woman, systemic features |
| Cryoglobulinaemia | ↓C3, ↓↓C4 | − | − | − | + | Granular | Purpura, neuropathy, HCV+ |
| IgA nephropathy | Normal | − | − | − | − | Mesangial IgA | Synpharyngitic haematuria |
| ANCA vasculitis | Normal | + | − | − | − | Pauci-immune | ENT/pulmonary/skin vasculitis |
| Anti-GBM disease | Normal | ± | + | − | − | Linear IgG | Pulmonary-renal syndrome |
| Membranous | Normal | − | − | − | − | Granular IgG/C3 (subepithelial) | Bland sediment, anti-PLA2R+ |
| MCD | Normal | − | − | − | − | Negative | Pure nephrotic, children |
The workup for glomerulonephritis includes: autoimmune markers (ANA, anti-dsDNA, C3/4, ANCA, anti-GBM, CRP, cryoglobulins), exclude infective causes (HBV/HCV/HIV/VDRL/malaria), malignancy screen (tumour markers, SIEP) especially in elderly, and renal biopsy (LM/IF/EM findings) → Diagnosis, guide treatment decisions and prognosis [17][18].
Don't Forget in the Elderly
A very common exam mistake: labelling an older patient's MPGN as "idiopathic" without screening for monoclonal gammopathy. In any patient over 40 with MPGN on biopsy, you must perform serum and urine immunofixation and serum free light chain ratio analysis — primary amyloidosis and light chain deposition disease are associated with a monoclonal gammopathy [9][10]. MGRS is increasingly recognized and treatable.
Age-stratified differential of glomerulonephritis [15]:
| Age Group | Nephrotic Presentation | Nephritic Presentation |
|---|---|---|
| < 15 years | MCD, FSGS | PSGN, IgA nephropathy / HSP |
| 15–40 years | MCD, FSGS, Membranous | IgA nephropathy, PSGN, Lupus nephritis, RPGN |
| > 40 years | MCD, Membranous, DM, Amyloidosis | PSGN, IgA nephropathy, RPGN |
MPGN can appear at any age but is not the commonest cause in any age group — it is always a "must-consider" differential rather than the leading diagnosis. C3 glomerulopathy/DDD tends to present in children/young adults, whereas immune complex-mediated MPGN (especially HCV-associated or MGRS) is more common in adults.
High Yield Summary — Differential Diagnosis of MPGN
-
The clinical presentation of MPGN (mixed nephrotic-nephritic with low complement) must be differentiated from: PSGN, lupus nephritis, IgA nephropathy, cryoglobulinaemia, ANCA vasculitis, anti-GBM disease, membranous nephropathy, and MCD/FSGS.
-
Complement levels are the most powerful bedside discriminator:
- ↓C3 only → PSGN (transient), C3G, infective endocarditis GN
- ↓C3 + ↓C4 → Lupus, IC-MPGN, cryoglobulinaemia
- Normal complement → IgA nephropathy, ANCA vasculitis, anti-GBM, MCD, FSGS, membranous
-
Persistent low C3 > 8 weeks → think MPGN or lupus nephritis, NOT PSGN
-
Once MPGN pattern is confirmed on biopsy, IF determines the category:
- Ig + C3 → Immune complex-mediated → search for HCV, HBV, SLE, cryoglobulinaemia, MGRS
- C3-dominant → C3 Glomerulopathy → complement studies (C3NeF, Factor H, genetic testing)
-
In elderly patients with MPGN: always screen for monoclonal gammopathy (SIEP, UIEP, serum free light chains)
-
Renal biopsy (LM/IF/EM) is essential for definitive diagnosis and to guide treatment
Active Recall - DDx of MPGN
References
[2] Senior notes: Ryan Ho Urogenital.pdf (p54 — Classification of GN by cellularity) [3] Senior notes: Block A – Nephrology Data Interpretation.pdf (p17 — Clinical presentation table of GN) [4] Senior notes: Ryan Ho GI.pdf (p232 — HCV extrahepatic manifestations including MPGN) [5] Lecture slides: GC 046. Facial rash and painful fingers_SLE.pdf [6] Lecture slides: GC 030. An old man with bone pain and anaemia.pdf [7] Senior notes: Block A - Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p19 — Persistently low C3) [9] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1008 — Biochemical tests for GN diagnosis) [10] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p433 — Nephrotic syndrome diagnosis, C3/C4 levels) [11] Senior notes: Adrian Lui Pediatrics Notes.pdf (p328 — PSGN clinical features and DDx) [12] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p420 — PSGN epidemiology) [13] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p998 — MPGN description, etiology, morphology) [14] Senior notes: Block A - Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p9 — Glomerular causes of haematuria) [15] Senior notes: Maksim Medicine Notes.pdf (p231–233 — GN nephrotic/nephritic features, age-stratified DDx) [16] Senior notes: Ryan Ho Urogenital.pdf (p64 — RPGN classification by IF) [17] Lecture slides: Introduction-kidney-Ix.pdf (p23 — Workup for glomerulonephritis) [18] Lecture slides: Nephrology - ntroduction to Renal Investigation.pdf (p23 — Workup for glomerulonephritis) [19] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p405 — MPGN etiology by type)
Diagnostic Criteria, Algorithm & Investigations for MPGN
Here is an important concept to grasp: MPGN does not have a single set of clinical diagnostic criteria like, say, the Jones criteria for rheumatic fever or the ACR/EULAR criteria for SLE. Why? Because MPGN is a histopathological pattern, not a clinical diagnosis. You cannot "diagnose" MPGN from bloodwork alone — you need tissue.
The diagnostic process for MPGN therefore has three sequential layers:
- Clinical suspicion — Recognizing a clinical syndrome consistent with glomerulonephritis (haematuria + proteinuria + renal impairment ± hypertension ± oedema) with hypocomplementaemia
- Serological workup — Narrowing the differential and identifying the underlying driver before biopsy
- Renal biopsy (definitive diagnosis) — LM/IF/EM to confirm the MPGN pattern and classify the underlying mechanism
Renal biopsy is still essential for definitive diagnoses of a number of renal diseases — including membranoproliferative GN [8].
Renal biopsy: LM/IF/EM findings → Diagnosis, guide treatment decisions and prognosis [17][18].
Key Principle — No Biopsy, No Definitive Diagnosis
Unlike PSGN (where biopsy is usually NOT done because the disease is self-limiting and the clinical picture + serology are sufficient [7][11]), MPGN requires renal biopsy for definitive diagnosis. The biopsy does three things: (1) confirms the MPGN histological pattern, (2) determines whether it is immune complex-mediated or complement-mediated via IF, and (3) guides treatment strategy.
2. The Diagnostic Algorithm — Step by Step
Let me walk you through this the way you'd approach it on a ward round, from the moment the patient walks in to the final pathological diagnosis.
The patient has some combination of:
- Haematuria (macro or micro, glomerular type — dysmorphic RBCs, RBC casts)
- Proteinuria (subnephrotic to nephrotic range)
- Renal impairment (rising creatinine/falling GFR)
- Hypertension
- Oedema
Diagnosis of renal diseases for specific treatment begins with clinical history and manifestation: oliguria or anuria, haematuria, proteinuria, oedema, hypertension, loin pain [8].
You recognize this is a glomerulonephritis. Now the question is: which one?
Basic laboratory investigations: blood for renal function test (urea and creatinine concentration), urine for microscopy (red cells and white cells), urine for quantification of protein (e.g. 24-hour urine for protein) [8].
Serum complement level is important in helping narrow the differential diagnosis [20][21].
↓C3/C4 generally indicate immune complex-mediated GN — DDx: MPGN, PSGN, lupus, cryoglobulinaemia, infective endocarditis and shunt nephritis [20][21].
Normal C3/C4 generally indicate non-immune-complex-mediated GN (except IgA nephropathy) — DDx: PAN, Goodpasture, HSP/IgAN, ANCA-related renal vasculitis [20][21].
This is where MPGN enters the differential — if complement is low.
Once biopsy confirms MPGN pattern:
- IF: Ig + C3 → Immune complex-mediated MPGN → search systematically for the underlying cause
- IF: C3-dominant, Ig-negative → C3 Glomerulopathy → proceed to complement studies
4. Investigation Modalities — Detailed Breakdown
I'll organize this as you would order them in clinical practice: bedside → bloods → urine → serology → imaging → biopsy.
| Investigation | What to Look For | Interpretation in MPGN | Mechanism |
|---|---|---|---|
| Urine dipstick | Blood, protein | Blood 2–3+, protein 2–3+ | GBM damage → haematuria + proteinuria |
| Urine microscopy | Dysmorphic RBCs, RBC casts | Present — confirms glomerular origin of haematuria [20][21] | RBCs deform as they squeeze through damaged GBM; casts form when RBCs are trapped in Tamm-Horsfall protein in tubules |
| Phase-contrast microscopy | Acanthocytes ( > 5%) | Highly specific for glomerular bleeding | Spiculated RBCs = passed through damaged GBM |
| Urine protein quantification | 24-hour urine protein or spot urine protein:creatinine ratio (uPCR) or albumin:creatinine ratio (ACR) | Can be subnephrotic or nephrotic range (> 3.5 g/day). MPGN shows proteinuria ++, nephrotic ++ [3] | GBM structural disruption + podocyte injury → loss of size/charge barrier |
| Urine sediment | WBCs, WBC casts, oval fat bodies | Sterile pyuria may be present; oval fat bodies if nephrotic range proteinuria | Inflammatory cells in glomerulus spill into urine; lipiduria from filtered lipoproteins |
Glomerular vs Non-Glomerular Haematuria
All haemoglobin-positive dipsticks must be accompanied by urine microscopy. Dysmorphic RBCs and RBC casts = glomerular disease. Isomorphic RBCs = urological disease (stones, tumour, infection). This distinction is fundamental and will appear in exams [20].
| Investigation | Expected Finding in MPGN | Why You Order It |
|---|---|---|
| RFT (urea, creatinine, eGFR) | Variable ↓GFR — creatinine may be mildly elevated or significantly raised depending on severity [8][20] | Quantify degree of renal impairment; baseline for monitoring |
| CBC | Normocytic normochromic anaemia (anaemia of CKD); ± thrombocytosis (nephrotic syndrome) [20] | Anaemia = chronic disease/CKD; thrombocytopenia may suggest TMA or SLE |
| Serum albumin | Low if nephrotic syndrome ( < 30 g/L) | Hypoalbuminaemia is one of the criteria that defines nephrotic syndrome [10] |
| Lipid profile | Elevated cholesterol/TG if nephrotic | Liver upregulates lipoprotein synthesis to compensate for urinary protein loss |
| ESR / CRP | Usually elevated | Non-specific marker of inflammation; helps distinguish active disease from chronic scarring |
| Blood glucose / HbA1c | To exclude diabetic nephropathy | Diabetic nephropathy is the commonest cause of CKD and can mimic nephrotic presentation [22] |
This is where MPGN stands out from most other GNs.
| Investigation | Expected in IC-MPGN | Expected in C3G/DDD | Why |
|---|---|---|---|
| Serum C3 | ↓ | ↓↓ (often profoundly) | Hypocomplementaemia is the diagnostic hallmark of MPGN [13][19]. IC-MPGN: classical pathway consumption. C3G: alternative pathway consumption |
| Serum C4 | ↓ (classical pathway activation) | Normal (alternative pathway only) | C4 is consumed only in the classical pathway. This helps distinguish the mechanism |
| CH50 (total haemolytic complement) | ↓ | ↓ | Measures overall complement function — reduced in any pathway activation |
GC 057 High Yield: "Total haemolytic complement activity and C3 concentrations are depressed. Persistently low C3 > 8 weeks raises the possibility of lupus nephritis or membranoproliferative glomerulonephritis." [23]
Advanced complement studies (for C3 Glomerulopathy workup):
| Test | What It Detects | Interpretation |
|---|---|---|
| C3 nephritic factor (C3NeF) | Autoantibody that stabilizes C3 convertase | Positive in ~80% of DDD and ~50% of C3GN — confirms autoimmune complement dysregulation |
| Factor H level / anti-Factor H antibodies | Deficiency or inhibition of the main fluid-phase regulator of the alternative pathway | Low Factor H or positive anti-Factor H Ab → uncontrolled alternative pathway activation |
| Factor I, Factor B, MCP/CD46 | Other complement regulatory proteins | Deficiency → predisposition to C3G |
| Genetic complement panel | Mutations in CFH, CFI, CFB, C3, CFHR genes | Identifies heritable complement dysregulation — important for prognosis and family screening |
| Soluble C5b-9 (membrane attack complex) | Terminal complement activation | Elevated → supports ongoing complement-mediated injury |
When to Order Advanced Complement Studies
You don't order C3NeF or genetic panels on everyone. These are reserved for when the renal biopsy shows C3-dominant IF staining (i.e., C3 Glomerulopathy is confirmed). The purpose is to identify the specific complement defect, which has implications for prognosis, recurrence risk post-transplant, and potential complement-targeted therapy.
Serology for relevant conditions [20][21]:
| Investigation | Purpose | Expected Result in Primary MPGN | Notes |
|---|---|---|---|
| ANA, anti-dsDNA | Lupus nephritis [9][10] | Negative | If positive → lupus nephritis causing MPGN pattern |
| ANCA (c-ANCA/PR3, p-ANCA/MPO) | ANCA vasculitis (GPA, MPA, EGPA) [9] | Negative | ANCA vasculitis is pauci-immune; different mechanism entirely |
| Anti-GBM antibody | Anti-GBM disease / Goodpasture [9] | Negative | If positive → linear IF, pulmonary-renal syndrome |
| HBsAg, anti-HCV, HCV RNA | HBV/HCV-related MPGN [9][17] | May be positive | HCV most often induces MPGN; HBV most often induces membranous nephropathy [9]. A positive serological test does NOT prove renal disease is due to HBV/HCV [9] — biopsy correlation needed |
| HIV serology | HIV nephropathy (collapsing FSGS) [9] | Negative | Part of standard screen |
| VDRL | Syphilis (associated with membranous nephropathy) [9] | Negative | Serological testing generally NOT performed until renal biopsy results are known [9] |
| Serum cryoglobulins (cryocrit) | Cryoglobulinaemia [9][20] | May be positive if HCV-associated | Presence of measurable cryoglobulin (cryocrit) is the most prominent laboratory hallmark of cryoglobulinaemia syndromes [9]. MUST keep specimen at 37°C during transport or cryoglobulins precipitate and give false negative! |
| ASO titre | PSGN [7][20] | Not elevated | Antibodies to streptolysin O may be raised in PSGN, but not all strains produce streptolysin O [7][23] |
| SIEP/UIEP + serum free light chains | Monoclonal gammopathy (MGRS/myeloma) [9][17][18] | May detect monoclonal band | Malignancy screen (e.g. tumour markers, SIEP) especially in elderly [17][18]. Primary amyloidosis and light chain deposition disease are associated with a monoclonal gammopathy [9] |
| Blood cultures | Infective endocarditis [20] | Negative (unless IE is the cause) | Order if persistent fever + murmur |
The Systematic Screen — Don't Miss Anything
A very common exam and clinical error is failing to perform the full panel. Even if the clinical picture strongly suggests one diagnosis, you must exclude the others. The mnemonic for the MPGN workup panel:
"CAVE HIM"
- Complement (C3, C4, CH50)
- Autoantibodies (ANA, anti-dsDNA, ANCA, anti-GBM)
- Viral serology (HBV, HCV, HIV)
- Electrophoresis (SIEP, UIEP, serum free light chains)
- History of infection (ASO, blood cultures, throat swab)
- Immunoglobulins (cryoglobulins, serum Ig levels)
- Malignancy screen (especially in elderly)
| Investigation | Purpose | Expected Finding in MPGN | When to Order |
|---|---|---|---|
| Renal ultrasound (USG) | Assess kidney size, exclude obstruction, rule out structural causes | Normal-sized or slightly enlarged kidneys in active MPGN; small, atrophic kidneys suggest chronic irreversible disease (biopsy usually NOT helpful) [21] | Always — before biopsy to confirm two kidneys of adequate size and no contraindications |
| CXR | Pulmonary involvement, fluid overload | Pulmonary oedema if fluid-overloaded; pulmonary infiltrates/haemorrhage if Goodpasture/vasculitis | If respiratory symptoms or to assess fluid status |
| CT thorax / DLCO | Pulmonary involvement if cough ± haemoptysis [20][21] | Abnormal if pulmonary-renal syndrome (Goodpasture, vasculitis) | If haemoptysis or unexplained dyspnoea |
| Echocardiogram | Infective endocarditis if persistent fever + murmur [20][21] | Vegetations if IE is the underlying cause | If IE is clinically suspected |
Renal biopsy is still essential for definitive diagnoses of membranoproliferative GN [8].
Why biopsy? Because:
- You cannot distinguish MPGN from other GNs clinically
- The IF pattern determines whether it is immune complex-mediated vs complement-mediated
- The EM pattern determines the subtype (DDD vs C3GN)
- Histological findings guide treatment and prognosis
Contraindications to percutaneous renal biopsy [24]:
- Bleeding diathesis
- Severe uncontrolled hypertension
- Solitary kidney
- Small kidneys indicative of chronic irreversible disease
- Hydronephrosis
- Renal or perirenal infection
How it's done: Percutaneous ultrasound-guided biopsy of the lower pole of the kidney (to avoid major vessels). Typically obtain 2 cores — one for LM/IF, one for EM.
What to look for on biopsy and the expected findings in MPGN:
| Modality | Findings in MPGN | Significance |
|---|---|---|
| Light Microscopy (LM) | Thickening of GBM [13][19] + Hypercellularity: proliferation of endothelial and mesangial cells, infiltration of leukocytes [13][19] + Lobular accentuation of glomerular tuft + "Tram-track" / "double contour" appearance on PAS/silver stain (due to mesangial interposition) + ± Crescent formation (if severe) | Confirms the MPGN morphological pattern. The lobular, proliferative appearance with GBM duplication is the sine qua non |
| Immunofluorescence (IF) | IC-MPGN: Granular deposits of complement (C3, C1q) + immunoglobulins (IgG, IgM) along capillary walls and mesangium [13][19] | The IF pattern is the KEY discriminator: Ig + C3 = immune complex-mediated. C3-dominant = C3 glomerulopathy. This determines the entire downstream workup and management |
| C3 Glomerulopathy: Dominant C3 staining, absent or trace Ig (C3 intensity ≥ 2 orders of magnitude > any Ig) | ||
| Electron Microscopy (EM) | IC-MPGN Type I: Subendothelial deposits [13][19] | Deposit location determines the old "type" classification. Subendothelial = Type I (commonest). Intramembranous = DDD (Type II). Subendothelial + subepithelial = Type III |
| DDD (old Type II): Intramembranous dense deposits — highly electron-dense ribbon-like deposits within the lamina densa of the GBM [13][19] | Virtually pathognomonic of DDD. These are so characteristic they are recognizable at a glance | |
| C3GN: Variable location deposits (mesangial, subendothelial, subepithelial) — NOT the classic dense-deposit pattern | Distinguishes C3GN from DDD within the C3G category |
GC 057 High Yield — Primary kidney diseases that can cause nephrotic syndrome include: focal segmental glomerulosclerosis, membranous glomerulopathy, minimal change disease, membranoproliferative glomerulonephritis, and occasionally IgA nephropathy [23].
Once biopsy is done, the pathologist reports back. Here is how you interpret it:
| IF Finding | Diagnosis | Next Step |
|---|---|---|
| Ig + C3 (granular, capillary wall + mesangial) | Immune complex-mediated MPGN | Search for secondary cause: HCV (with cryoglobulins?), HBV, SLE, MGRS, IE, malignancy |
| C3-dominant, Ig-negative/trace | C3 Glomerulopathy | EM to subclassify → DDD vs C3GN. Then: complement studies (C3NeF, Factor H, genetic panel) |
| "Full house" (IgG, IgA, IgM, C3, C1q) | Lupus nephritis (MPGN pattern) | Confirm with clinical criteria + ANA/anti-dsDNA. Classify ISN/RPS class |
| Ig + C3 with organized deposits (fibrillar/microtubular) | Cryoglobulinaemic GN or immunotactoid GN | Check cryocrit, HCV status. EM: organized deposits (fibrils ~20 nm for cryo, ~30–50 nm for immunotactoid) |
| Monotypic Ig (single light chain class) | MGRS-associated MPGN | Haematology referral. Confirm with SIEP/UIEP/serum free light chains. Bone marrow biopsy |
| Category | Tests | Rationale |
|---|---|---|
| Urinalysis | Dipstick, microscopy, uPCR/24h protein | Confirm glomerular haematuria and quantify proteinuria |
| Basic bloods | RFT, CBC, albumin, lipids, glucose | Assess renal function, nephrotic features, exclude DM |
| Complement | C3, C4, CH50 | The single most important serological discriminator for MPGN |
| Autoimmune | ANA, anti-dsDNA, ANCA, anti-GBM | Exclude lupus, vasculitis, anti-GBM disease |
| Infection screen | HBV, HCV, HIV, VDRL, ASO, blood cultures | Exclude infection-driven immune complex MPGN |
| Paraprotein screen | SIEP, UIEP, serum free light chains | Exclude MGRS/myeloma (especially in elderly) |
| Cryoglobulins | Cryocrit | Exclude cryoglobulinaemia (often HCV-associated) |
| Imaging | Renal USG, CXR, ± echo | Kidney size (biopsy feasibility), fluid status, exclude IE |
| Renal biopsy | LM, IF, EM | Definitive diagnosis. IF pattern classifies the mechanism |
| Complement studies (if C3G) | C3NeF, Factor H/I/B, genetic panel | Identify specific complement defect for targeted therapy |
High Yield Summary — Diagnosis of MPGN
-
MPGN is a histopathological diagnosis — there are no standalone clinical diagnostic criteria. Definitive diagnosis requires renal biopsy with LM/IF/EM.
-
Clinical clues raising suspicion: Mixed nephrotic-nephritic picture + persistently low C3 (> 8 weeks) + active urine sediment.
-
Pre-biopsy workup (mnemonic "CAVE HIM"): Complement, Autoantibodies, Viral serology, Electrophoresis/paraprotein, History of infection, Immunoglobulins/cryoglobulins, Malignancy screen.
-
IF is the KEY discriminator on biopsy:
- Ig + C3 → Immune complex-mediated → hunt for HCV, HBV, SLE, cryoglobulinaemia, MGRS
- C3-dominant → C3 Glomerulopathy → complement studies (C3NeF, Factor H, genetics)
-
EM subclassifies C3G: DDD (intramembranous dense deposits) vs C3GN (variable location deposits).
-
Do NOT forget paraprotein screen in elderly patients — MGRS is treatable and commonly missed.
-
Complement pattern:
- ↓C3, ↓C4 = classical pathway = IC-MPGN, lupus, cryoglobulinaemia
- ↓↓C3, normal C4 = alternative pathway = C3 Glomerulopathy
- Transient ↓C3 (normalizes ≤ 8 wk) = PSGN
Active Recall - Diagnosis of MPGN
References
[3] Senior notes: Block A – Nephrology Data Interpretation.pdf (p17 — Clinical presentation table of GN) [7] Senior notes: Block A - Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p19 — Persistently low C3, PSGN investigations) [8] Senior notes: Block A - Nephrotology Teaching Clinic RTD.pdf (p3–4 — Diagnosis of renal diseases, renal biopsy essential for MPGN) [9] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1008 — Biochemical tests for GN diagnosis) [10] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p433 — Nephrotic syndrome diagnosis, C3/C4 levels) [11] Senior notes: Adrian Lui Pediatrics Notes.pdf (p328 — PSGN clinical features and DDx) [13] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p998 — MPGN description, etiology, morphology) [17] Lecture slides: Introduction-kidney-Ix.pdf (p23 — Workup for glomerulonephritis) [18] Lecture slides: Nephrology - ntroduction to Renal Investigation.pdf (p23 — Workup for glomerulonephritis) [19] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p405 — MPGN etiology and morphology by type) [20] Senior notes: Ryan Ho Urogenital.pdf (p63 — Evaluation of nephritic syndrome, serology workup) [21] Senior notes: Adrian Lui Pediatrics Notes.pdf (p325 — Evaluation of nephritic syndrome) [22] Senior notes: Block A - Chronic Kidney Disease and its Complications.pdf (p8 — Causes of CKD) [23] Lecture slides: GC 057. Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p8, p9, p36, p41) [24] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p770 — Renal biopsy contraindications)
Management of MPGN
This is the single most important concept for managing MPGN: MPGN is a histological pattern, not a disease. Therefore, management is fundamentally determined by the underlying cause identified through the diagnostic workup and renal biopsy. There is no single "MPGN protocol" — the treatment differs dramatically depending on whether you are dealing with HCV-associated cryoglobulinaemic MPGN, lupus nephritis presenting as MPGN, MGRS-driven MPGN, or idiopathic C3 glomerulopathy.
Treat underlying cause. Idiopathic MPGN: steroid ± cyclophosphamide (if deteriorating renal function) [15].
1. Supportive Care — For ALL Patients With MPGN
Regardless of the underlying cause, every patient with MPGN receives supportive care. These measures are common to all glomerulonephropathies and are frequently tested in SAQs.
General management of nephrotic/nephritic syndrome (SAQ!) [15]:
| Parameter | Method | Rationale |
|---|---|---|
| I/O (intake/output) | Fluid balance chart | Detect fluid overload or hypovolaemia from over-diuresis |
| Vitals | BP, HR, temp, SpO2 | Hypertension monitoring is critical — drives progressive renal damage |
| Body weight daily | Aim ~1 kg/day loss if oedematous [15] | Weight gain = fluid retention. Too rapid diuresis → hypovolaemia → pre-renal AKI |
| Urine dipstick | Daily in acute phase | Track proteinuria and haematuria trends |
| RFT | Serial (daily if AKI, otherwise weekly–fortnightly) | Detect deteriorating renal function early |
Monitoring of blood pressure and body weight, home urine dipstick monitoring [25].
| Intervention | Details | Mechanism | Cautions |
|---|---|---|---|
| Low sodium diet | Na+ restriction to max 2 g/day [25] | Reduces tubular sodium reabsorption → less water retention → less oedema | Must be balanced with nutritional needs |
| Fluid restriction | ~50% maintenance if severe oedema [25] | Reduces intravascular volume addition | Generally not needed unless severe |
| Diuretics | High-dose frusemide ± thiazide ± spironolactone [15] | Frusemide (loop diuretic) blocks NKCC2 in thick ascending limb → natriuresis. Adding thiazide (blocks NCC in DCT) provides sequential nephron blockade for synergistic effect. Spironolactone (blocks aldosterone receptor in collecting duct) → K+-sparing + additional natriuresis | Furosemide ± spironolactone ONLY indicated in severe symptomatic oedema with normal intravascular status [25]. May precipitate hypovolaemic shock, AKI, and increased thrombosis risk in patients with marked hypoalbuminaemia and intravascular volume depletion |
Why is diuretic use tricky in nephrotic syndrome? In nephrotic patients, the low albumin means oncotic pressure is already reduced, so intravascular volume may be DECREASED even though total body water is INCREASED (oedema). Aggressive diuresis can cause intravascular depletion → pre-renal AKI. Think of it as: the water is in the wrong compartment.
Albumin infusion: Reserved as adjunct to diuretics only for diuretic-resistant oedema with oliguria/uraemia in the absence of severe glomerular damage [26]. IV albumin transiently raises oncotic pressure, pulling fluid back into the intravascular space, but is quickly lost in the urine due to the leaky GBM — so the benefit is short-lived.
Anti-proteinuric drugs (ACEI/ARB): for ALL glomerulopathies — ↓glomerular pressure, ↓rate of GFR decline [15].
| Drug Class | Examples | Mechanism | Target | Contraindications |
|---|---|---|---|---|
| ACEI | Ramipril, perindopril, lisinopril | Inhibits ACE → ↓angiotensin II → preferential efferent arteriolar dilation → ↓intraglomerular pressure → ↓filtration pressure across the GBM → ↓proteinuria | Proteinuria < 1 g/day or uPCR < 0.5–1 g/g [26] | Bilateral renal artery stenosis (removes the efferent arteriolar tone that maintains GFR in the setting of poor renal perfusion → precipitous GFR drop) [27]; hyperkalaemia; pregnancy |
| ARB | Losartan, valsartan, irbesartan | Blocks AT1 receptor → same downstream effect as ACEI on efferent arteriole | Same as ACEI | Same as ACEI |
Why do they work? Angiotensin II normally constricts the efferent arteriole more than the afferent. This maintains intraglomerular pressure (useful in dehydration). In glomerular disease, this high pressure is harmful — it pushes more protein across the damaged GBM. By blocking angiotensin II, you dilate the efferent arteriole → drop intraglomerular pressure → less "force" pushing protein through → less proteinuria → slower progression.
ACEI or ARB is a compelling indication in both diabetes and chronic kidney disease [28].
Never Combine ACEI + ARB
Never prescribe ACEI and ARB together — this has been shown to cause more harm (hyperkalaemia, AKI) without benefit in multiple trials (ONTARGET, VA NEPHRON-D) [27].
Statins: if hyperlipidaemia persists after treatment [15].
| Drug | Indication | Mechanism |
|---|---|---|
| Statins (atorvastatin, rosuvastatin) | Persistent hyperlipidaemia despite treatment of underlying nephrotic syndrome | HMG-CoA reductase inhibition → ↓hepatic cholesterol synthesis → ↓LDL. In nephrotic syndrome, the liver upregulates lipoprotein production to compensate for urinary albumin loss. Statins counteract this and reduce long-term cardiovascular risk |
DVT prophylaxis: compressive stockings ± anticoagulation if high risk [15].
Why are nephrotic patients hypercoagulable? Because:
- Urinary loss of antithrombin III (a natural anticoagulant — small enough to be filtered through damaged GBM)
- Compensatory hepatic upregulation of procoagulant factors (fibrinogen, factors V, VII, VIII)
- Thrombocytosis (reactive)
- Hyperviscosity from haemoconcentration
| Intervention | Indication | Notes |
|---|---|---|
| Compression stockings | All immobilized nephrotic patients | Low-risk, non-pharmacological |
| Therapeutic anticoagulation | Usually only if thromboembolic events occur [26] | Not routinely prophylactic |
| Prophylactic anticoagulation | High-risk patients: very low albumin ( < 20 g/L), membranous nephropathy, prolonged immobility [26] | Risk-benefit must be weighed against bleeding risk |
Pneumococcal vaccination is indicated for ALL patients with nephrotic syndrome because urinary loss of immunoglobulins increases susceptibility to encapsulated organisms (especially Streptococcus pneumoniae) [26].
2. Cause-Specific Treatment — The Critical Layer
This is one of the most common identifiable causes of immune complex-mediated MPGN, especially in adults. The treatment has been revolutionized by direct-acting antivirals (DAAs).
| Treatment | Details | Mechanism | When to Use |
|---|---|---|---|
| Direct-acting antivirals (DAAs) | Sofosbuvir-based regimens (e.g., sofosbuvir/velpatasvir for 12 weeks) | Directly inhibit HCV replication → ↓viral load → ↓immune complex formation → ↓glomerular deposition → disease remission | First-line for ALL HCV-associated MPGN. Achieves sustained virological response (SVR) in > 95%. SVR leads to renal improvement in most patients |
| Rituximab | Anti-CD20 monoclonal antibody | Depletes B cells → ↓cryoglobulin-producing B-cell clones → ↓immune complex formation | Added to DAAs if severe cryoglobulinaemic vasculitis (progressive renal failure, skin vasculitis, neuropathy) |
| Plasmapheresis | Removes circulating cryoglobulins and immune complexes | Rapid reduction of pathogenic circulating proteins | Life-threatening cryoglobulinaemic flare (e.g., rapidly progressive GN, pulmonary haemorrhage) — bridge while waiting for DAA/rituximab to take effect |
| Avoid interferon-based regimens | Old standard; no longer first-line | Interferon can exacerbate cryoglobulinaemia and autoimmunity | Superseded by DAAs |
DAA Revolution
Before 2014, HCV-associated MPGN was treated with interferon + ribavirin (poor cure rates, significant toxicity). DAAs have transformed outcomes: > 95% SVR, well-tolerated, shorter courses. If SVR is achieved and cryoglobulinaemia resolves, the MPGN often remits completely.
| Treatment | Details | Notes |
|---|---|---|
| Antiviral therapy | Entecavir or tenofovir alafenamide (TAF) | Suppresses HBV replication → ↓HBsAg-HBsAb immune complex formation. Tenofovir disoproxil fumarate (TDF) has renal tubular toxicity risk; TAF is preferred for renal safety [29] |
| Avoid immunosuppression alone | Steroids/cyclophosphamide without antivirals can cause HBV reactivation and hepatic flare | Always start antivirals BEFORE or concurrently with any immunosuppression |
SLE management depends on severity [30]:
| Severity | Regimen |
|---|---|
| Induction (Class III/IV LN — the types producing MPGN pattern) | HCQ (for ALL SLE patients) + IV pulse methylprednisolone 0.5–1 g/day × 3 days followed by oral prednisolone taper + MMF (mycophenolate mofetil) or IV cyclophosphamide [30] |
| Maintenance | HCQ + low-dose steroids + MMF (preferred) or azathioprine [30] |
| Refractory | Rituximab (anti-CD20) or belimumab (anti-BAFF) [30] |
Why MMF? Mycophenolate (myco = fungal origin, phenolate = phenolic acid derivative) inhibits inosine monophosphate dehydrogenase → blocks de novo purine synthesis → selectively suppresses lymphocyte proliferation (lymphocytes depend on de novo pathway more than other cells which can use salvage pathway). This makes it relatively lymphocyte-selective with fewer side effects than cyclophosphamide.
Why cyclophosphamide? An alkylating agent that cross-links DNA → prevents cell replication. Potent but toxic: risk of haemorrhagic cystitis (prevent with mesna + hydration), infection (PCP prophylaxis with co-trimoxazole), gonadal toxicity (fertility preservation discussion essential), and malignancy. Reserved for severe or refractory disease.
| Treatment | Details | Rationale |
|---|---|---|
| Clone-directed therapy | Haematology referral. Regimens depend on the clone type: bortezomib-based (if plasma cell), rituximab-based (if B-cell), or other chemotherapy | The principle is to eliminate the B-cell/plasma cell clone producing the pathogenic monoclonal immunoglobulin. If you eliminate the source, the immune complex deposition stops and the kidney can recover |
| Avoid "watch and wait" | Unlike MGUS (which is benign), MGRS causes organ damage — even though the clone is small | MGRS is defined by the presence of renal damage attributable to the monoclonal protein. It needs treatment even if haematological criteria for myeloma/lymphoma are not met |
| Treatment | Details |
|---|---|
| Prolonged IV antibiotics | Treat the endocarditis per guidelines (typically 4–6 weeks of bactericidal IV antibiotics). Once infection is eradicated, the antigenemia resolves → immune complex deposition stops → GN improves |
| Surgery | If valve destruction, heart failure, or persistent bacteraemia |
When the full workup is negative for secondary causes:
Idiopathic MPGN: steroid ± cyclophosphamide (if deteriorating renal function) [15].
| Treatment | Indication | Regimen | Evidence |
|---|---|---|---|
| Supportive care only | Mild disease: stable renal function, subnephrotic proteinuria | ACEI/ARB + BP control + monitoring | Reasonable approach given limited evidence for immunosuppression in idiopathic IC-MPGN |
| Corticosteroids | Nephrotic syndrome and/or progressive renal impairment | Oral prednisolone (starting dose ~1 mg/kg/day, taper over months) | Limited evidence; some observational studies suggest benefit |
| Cyclophosphamide | Deteriorating renal function despite steroids [15] | Added to steroid regimen (oral or IV pulse) | Used as second-line escalation; significant toxicity (haemorrhagic cystitis, infection, gonadotoxicity) |
| MMF | Alternative to cyclophosphamide (less toxic) | Used increasingly in practice as a steroid-sparing agent | Small case series; no RCTs |
Evidence Gap — Honest Assessment
The evidence base for immunosuppressive treatment of idiopathic MPGN is weak. There are no large randomized controlled trials. Most data comes from small observational studies and case series. KDIGO 2021 guidelines recommend a cautious approach: supportive care first, immunosuppression only if progressive disease. This contrasts with well-established protocols for lupus nephritis or ANCA vasculitis.
C3G is the trickiest to manage because it is driven by complement dysregulation, and conventional immunosuppression (designed to suppress immune cells) does not directly address the complement pathway defect.
| Treatment | Indication | Mechanism | Evidence Level |
|---|---|---|---|
| Supportive care + ACEI/ARB | All patients | Standard anti-proteinuric + renoprotective | Universally recommended |
| MMF | Progressive disease with active inflammation on biopsy | Suppresses lymphocyte proliferation; may reduce production of C3NeF (an autoantibody) | Observational; some patients respond |
| Corticosteroids | Active inflammatory disease | Anti-inflammatory | Variable response; some benefit reported |
| Eculizumab | Refractory progressive C3G, especially if terminal complement activation is prominent | Monoclonal antibody against C5 → blocks formation of membrane attack complex (C5b-9). "Eculizumab" = anti-C5 ("ecul-" from Latin equi- = "equal/block", targeting C5) | Case reports and small series; mixed results. Best evidence in patients with elevated soluble C5b-9. Not universally effective |
| Iptacopan / danicopan | Emerging complement-targeted therapies — Factor B inhibitors | Block Factor B → inhibit alternative pathway C3 convertase formation → reduce C3 activation | Phase 2/3 trials ongoing as of 2025–2026. Promising preliminary data |
| Anti-C3 therapy (pegcetacoplan) | Investigational for C3G | Monoclonal antibody/peptide targeting C3 directly | Early-phase trials |
| Plasmapheresis | C3G with C3NeF (autoantibody) — theoretically can remove the autoantibody | Removes circulating C3NeF | Limited evidence; used in acute flares |
Key point about C3G management: The field is rapidly evolving. Complement-targeted therapies represent a paradigm shift because they address the root cause (complement dysregulation) rather than non-specifically suppressing the immune system. However, as of 2026, evidence remains limited to small studies.
4. Management of Specific Complications
This can occur due to:
- Crescentic transformation (RPGN)
- Over-diuresis (hypovolaemia)
- Nephrotoxic drugs (NSAIDs, contrast)
Immediate approach to AKI [31]:
- Ensure ABC: "A dead person has no renal function"
- Treat hypoxaemia, treat hypotension with fluid resuscitation
- Consider and reverse nephrotoxic drugs (NSAIDs, aminoglycosides, ACEI/ARB)
- Manage life-threatening complications:
- Fluid overload → IV loop diuretics, dialysis
- Hyperkalaemia → IV calcium, insulin/dextrose, kayexalate, dialysis
- Metabolic acidosis → IV bicarbonate, dialysis
If RPGN (crescentic transformation): This is a medical emergency. Treatment follows RPGN protocols based on the IF pattern:
Indications for haemodialysis (mnemonic: AEIOU) [31]:
- Acidosis: metabolic acidosis pH < 7.1 refractory to bicarbonate
- Electrolytes: hyperkalaemia > 6.5 or rapidly rising, refractory to medical Rx
- Intoxication: drug removal in overdose
- Overload: fluid overload refractory to diuretics
- Uraemia: features of uraemia (pericarditis, neuropathy, encephalopathy)
MPGN has poor prognosis in general — 50% develop end-stage disease in 10 years after diagnosis [13][19].
Therapeutic objectives for CKD [22]:
- Delay kidney failure
- Control hypertension
- Reduce albuminuria
- Treat anaemia and MBD (mineral bone disease)
- Treat acidosis, hyperkalaemia
- Control lipids and cardiovascular risk
If progression to stage 5 CKD / ESRD despite all measures:
- Preparation for renal replacement therapy [32]
- Options: peritoneal dialysis, haemodialysis, or renal transplantation
A critically important point: MPGN has a high recurrence rate in the transplanted kidney, especially C3 Glomerulopathy.
| Type | Recurrence Risk Post-Transplant | Notes |
|---|---|---|
| IC-MPGN (secondary) | Low if underlying cause is treated (e.g., SVR for HCV, remission of SLE) | Address the cause before/during transplant |
| IC-MPGN (idiopathic) | Moderate (~30–50%) | May recur but usually less aggressive |
| C3 Glomerulopathy (C3GN) | ~50–70% | High recurrence risk because the complement defect is systemic, not confined to the native kidney |
| Dense Deposit Disease (DDD) | > 80% | Very high recurrence; DDD has the worst post-transplant prognosis of all GNs. The complement dysregulation continues to damage the graft |
Implications: Genetic complement testing before transplantation is essential for C3G patients. If a specific complement mutation is identified, targeted complement blockade (e.g., eculizumab prophylaxis) may be considered peri-transplant, though evidence is still evolving.
| MPGN Subtype | First-Line Treatment | Second-Line / Refractory | Key Principle |
|---|---|---|---|
| HCV ± cryoglobulinaemia | DAAs (sofosbuvir-based) ± rituximab | Plasmapheresis for severe cryo flare | Cure the virus → cure the MPGN |
| HBV | Entecavir or tenofovir (TAF) | — | Always antiviral before/with immunosuppression |
| Lupus nephritis | HCQ + steroids + MMF or cyclophosphamide | Rituximab, belimumab | Follow SLE nephritis protocols (ISN/RPS class) |
| MGRS | Clone-directed therapy (haem referral) | — | Eliminate the monoclonal clone |
| Infective endocarditis | Prolonged IV antibiotics ± surgery | — | Eradicate infection → GN resolves |
| Idiopathic IC-MPGN | Supportive + ACEI/ARB. Steroids if progressive | + Cyclophosphamide if deteriorating RFT [15] | Limited evidence; treat conservatively first |
| C3GN | Supportive + ACEI/ARB. MMF or steroids if progressive | Eculizumab (refractory); emerging Factor B inhibitors | Complement-targeted therapy is the future |
| DDD | Supportive + ACEI/ARB | Eculizumab (very variable response); complement studies to guide | Worst prognosis; highest transplant recurrence |
High Yield Summary — Management of MPGN
-
The overarching principle: TREAT THE UNDERLYING CAUSE. MPGN management is not one-size-fits-all.
-
Supportive care for ALL patients:
- ACEI/ARB (anti-proteinuric, renoprotective — for ALL glomerulopathies)
- Low sodium diet + diuretics (frusemide ± thiazide ± spironolactone) for oedema
- Statins if persistent hyperlipidaemia
- DVT prophylaxis
- Monitoring: I/O, BP, body weight (aim ~1 kg/day loss), urine dipstick, serial RFT
-
Cause-specific treatment:
- HCV → DAAs ± rituximab ± plasmapheresis
- HBV → Entecavir/TAF (always before immunosuppression)
- SLE → HCQ + steroids + MMF/cyclophosphamide
- MGRS → Clone-directed therapy
- IE → Prolonged antibiotics
- Idiopathic → Steroids ± cyclophosphamide if deteriorating RFT
-
C3 Glomerulopathy: Supportive + immunosuppression (MMF/steroids) for progressive disease; eculizumab for refractory cases; emerging complement-targeted therapies (Factor B inhibitors).
-
Prognosis: poor — 50% ESRD at 10 years. High transplant recurrence especially for DDD ( > 80%) and C3GN (~50–70%).
-
Never combine ACEI + ARB. Never immunosuppress HBV patients without antivirals. Never give NSAIDs to patients with renal impairment.
Active Recall - Management of MPGN
References
[8] Senior notes: Block A - Nephrotology Teaching Clinic RTD.pdf (p3–4 — Diagnosis of renal diseases, renal biopsy for MPGN) [13] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p998 — MPGN description, prognosis) [15] Senior notes: Maksim Medicine Notes.pdf (p231–233 — MPGN management, general nephrotic/nephritic management) [16] Senior notes: Ryan Ho Urogenital.pdf (p64 — RPGN management, empirical pulse methylprednisolone) [17] Lecture slides: Introduction-kidney-Ix.pdf (p23 — Workup for glomerulonephritis) [18] Lecture slides: Nephrology - ntroduction to Renal Investigation.pdf (p23 — Workup for glomerulonephritis) [19] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p405 — MPGN etiology, prognosis) [22] Senior notes: Block A - Chronic Kidney Disease and its Complications.pdf (p8, p17 — Causes of CKD, therapeutic objectives) [25] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p435 — General management of nephrotic syndrome) [26] Senior notes: Ryan Ho Fundamentals.pdf (p368 — General approach to nephrotic syndrome management) [27] Senior notes: Block A – Nephrology Data Interpretation.pdf (p11 — ACEI/ARB precautions, bilateral RAS) [28] Senior notes: Block A - High blood pressure_ hypertension.pdf (p42 — Compelling indications for ACEI/ARB) [29] Senior notes: Block A - Drugs and the Kidney.pdf (p9 — TDF renal toxicity, direct tubular toxicity) [30] Senior notes: Ryan Ho Rheumatology.pdf (p76 — SLE management by severity) [31] Senior notes: Ryan Ho Critical Care.pdf (p25–26 — AKI management, dialysis indications) [32] Senior notes: Block A - Glomerular and Tubulo-interstitial Diseases and Acute Kidney Injury.pdf (p28 — Chronic GN treatment principles)
Amyloidosis
Amyloidosis is a group of disorders characterised by extracellular deposition of insoluble amyloid fibrils in organs and tissues, leading to progressive organ dysfunction through pressure atrophy of adjacent cells.
Post-Streptococcal Glomerulonephritis
Post-streptococcal glomerulonephritis is an immune complex–mediated glomerulonephritis that develops as a delayed complication of nephritogenic Group A streptococcal infection, representing the prototypical acute nephritic syndrome.