Takayasu arteritis is a chronic granulomatous large-vessel vasculitis primarily affecting the aorta and its major branches, most commonly seen in young women, leading to arterial stenosis, occlusion, or aneurysm formation.

Exam domain	One-glance essentials
Definition / diagnosis	Takayasu arteritis is granulomatous large-vessel vasculitis of the aorta and major branches ^[1] Also called *pulseless disease / aortic arch syndrome* ^[1]
Epidemiology / risks	*Classically a young Asian woman, usually age 10–40* ^[1] Female:male ratio is approximately 8–9:1 in Asian cohorts ^[2]
Core mechanism	Granulomatous mural inflammation → intimal fibrosis → stenosis/occlusion and ischaemia ^[2] Medial destruction → aneurysm/aortic-root dilatation, regurgitation and rupture risk ^[2]
Clinical picture	*Bruits, limb claudication, reduced pulses and asymmetric arm blood pressure* ^[1] Renal-artery stenosis causes renovascular hypertension; constitutional inflammation may precede vascular symptoms ^[2]
Investigations	*Inflammatory markers plus aortography/MR angiography* are local lecture priorities ^[1] CTA/MRA maps wall thickening, stenosis and aneurysm; normal ESR/CRP does not reliably exclude active disease ^[2]
Management	*High-dose corticosteroid + steroid-sparing immunosuppression; anti-IL-6 for refractory disease* ^[1] Revascularise critical lesions preferably when inflammation is quiescent ^[2]
Complications	Renovascular hypertension, heart failure, aortic regurgitation, stroke/TIA and renal failure ^[3] Coronary ostial stenosis, pulmonary hypertension and aortic aneurysm/dissection ^[3]
Prevention / follow-up	Control BP and vascular risk; use serial vascular imaging to detect silent progression ^[2] Screen TB/HBV and provide bone protection before prolonged immunosuppression ^[2]
Exam traps	*Measure four-limb BP: subclavian stenosis may make an arm pressure falsely low ^[1] Differentiate from GCA by age (Takayasu < 50; GCA ≥ 50*); tocilizumab suppresses CRP, so monitor with imaging ^[1]^[2]

References

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (Takayasu arteritis, pp.89–90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (Takayasu Arteritis, p.96) ^[3] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (vasculitis comparison and vascular complications, pp.1763–1768)

Takayasu Arteritis

Takayasu arteritis (TA) is a chronic, idiopathic, granulomatous large vessel vasculitis that primarily affects the aorta and its major branches (and occasionally the pulmonary arteries). The inflammatory process causes segmental stenosis, occlusion, dilatation, and/or aneurysm formation of the affected vessels, leading to end-organ ischaemia.

Breaking down the name:

"Takayasu" — named after Dr. Mikito Takayasu, a Japanese ophthalmologist who first described the characteristic retinal arteriovenous anastomoses (1908)
"Arteritis" — "arter" = artery, "-itis" = inflammation; literally, inflammation of arteries

Also known as "pulseless disease", "aortic arch syndrome", and "occlusive thromboaortopathy" ^[1]

These synonyms tell you the clinical story:

Pulseless disease — the stenosed/occluded arteries lead to absent or diminished peripheral pulses
Aortic arch syndrome — the aortic arch and its branches are the most commonly affected segments
Occlusive thromboaortopathy — "occlusive" = blocking, "thrombo" = clot, "aorto" = aorta, "-pathy" = disease; a disease of the aorta causing occlusion

Key Distinction from GCA

Both Takayasu arteritis and Giant Cell Arteritis (GCA) are large vessel vasculitides with granulomatous histology. The classic teaching distinction is age: TA typically affects patients < 50 years, while GCA affects patients ≥ 50 years. When you see a young woman with absent pulses and bruits, think Takayasu. When you see an elderly patient with new headache and jaw claudication, think GCA. However, there is increasing evidence they may represent a disease spectrum.

2. Epidemiology

TA is an uncommon disease globally, with an estimated annual incidence of approximately 1–3 per million in most populations
However, incidence is significantly higher in Asian countries — Japan reports an incidence of ~40 per million, and it is one of the most recognised vasculitides in East Asia including Hong Kong, China, India, Korea, and Southeast Asia ^[1]^[2]
Prevalence estimates range from 4.7 to 40 per million depending on the population

Females of child-bearing age ^[1]: the overwhelming majority (80–90%) of patients are female
More common in Asians ^[1]
Age of onset: typically 10–40 years (peak in the 2nd–3rd decade of life), though cases can occur in children and older adults ^[2]
Female-to-male ratio: approximately 8–9:1 in Asian populations (slightly lower ~3:1 in Western cohorts)

Although no large-scale HK registry data exist, TA is well recognised among the local rheumatology and vascular surgery services
Given the Asian predominance, HK clinicians should maintain a high index of suspicion in young women presenting with unexplained hypertension, limb claudication, absent pulses, or constitutional symptoms
In HK, important differential diagnoses include atherosclerotic disease (common in the ageing population) and fibromuscular dysplasia (rare)

3. Anatomy and Function (Relevant Vascular Anatomy)

Understanding the anatomy is crucial because the clinical features of TA are entirely determined by which vessels are stenosed, occluded, or aneurysmal.

The aorta is the largest artery in the body. It can be divided into:

Ascending aorta → gives off the coronary arteries
Aortic arch → gives off (from right to left):
- Brachiocephalic trunk (→ right common carotid + right subclavian)
- Left common carotid artery
- Left subclavian artery
Descending thoracic aorta → intercostal arteries, bronchial arteries
Abdominal aorta → coeliac trunk, superior mesenteric artery (SMA), renal arteries, inferior mesenteric artery (IMA), then bifurcates into the common iliac arteries

The arterial wall has three layers:

Tunica intima (innermost) — endothelial cells; initial site of immune-mediated injury
Tunica media (middle) — smooth muscle and elastic fibres; the primary site of granulomatous inflammation in TA → destruction leads to aneurysm; reactive fibrosis leads to stenosis
Tunica adventitia (outermost) — connective tissue with vasa vasorum (the tiny vessels that supply blood to the arterial wall itself); the inflammatory process often begins here via activated dendritic cells around the vasa vasorum

TA is classified anatomically based on the distribution of arterial involvement:

Type	Vessels Involved
Type I	Aortic arch and its branches only
Type IIa	Ascending aorta, aortic arch, and branches
Type IIb	Type IIa + thoracic descending aorta
Type III	Thoracic descending aorta, abdominal aorta, and/or renal arteries
Type IV	Abdominal aorta and/or renal arteries only
Type V	Entire aorta and its branches (combined features of Types IIb + IV)

In Asian populations (including HK), Type I (aortic arch involvement) and Type V (extensive disease) are the most common patterns. Indian and Middle Eastern populations tend to have more abdominal aorta involvement (Types III–IV).

TA can also involve the pulmonary arteries (in up to 50% on imaging), which is unique among the large vessel vasculitides
This can cause pulmonary hypertension, dyspnoea, and occasionally haemoptysis

4. Etiology

The exact cause of Takayasu arteritis remains unknown (idiopathic). It is believed to result from an interplay of genetic susceptibility, immune dysregulation, and possible environmental triggers.

HLA associations: The strongest genetic association is with HLA-B*52:01, particularly in Japanese and other East Asian populations
- HLA-B*52 is present in ~40% of Japanese TA patients vs. ~10% of healthy controls
- This MHC class I association suggests a role for CD8+ cytotoxic T lymphocytes in disease pathogenesis
Other associated loci: IL12B, IL6, FCGR2A/3A, RPS9/LILRB3, and polymorphisms in the TNF gene region
Familial clustering has been reported, though TA is not a Mendelian disease

TA is fundamentally an autoimmune/autoinflammatory condition
The immune response is predominantly cell-mediated (Th1 and Th17 driven):
- Dendritic cells in the adventitia become activated (possibly by an unknown antigen)
- They recruit CD4+ and CD8+ T lymphocytes and macrophages to the vessel wall
- Macrophages differentiate into epithelioid cells and fuse to form multinucleated giant cells → forming granulomas
- These cells secrete matrix metalloproteinases (MMPs) and reactive oxygen species (ROS) → destroying the elastic lamina and media
- Pro-inflammatory cytokines (TNF-α, IL-6, IL-17, IFN-γ) drive the systemic and local inflammatory response
- IL-6 is particularly elevated and correlates with disease activity — this is the rationale for anti-IL-6 therapy (tocilizumab)

Tuberculosis (TB): A long-standing hypothesis, particularly relevant in Asia (including HK), based on:
- Epidemiological overlap between TB-endemic regions and TA prevalence
- Granulomatous histology shared between TB and TA
- Cross-reactivity between mycobacterial heat shock protein 65 (HSP65) and human HSP60/65 in the aortic wall (molecular mimicry)
- However, no definitive causal link has been proven; TB should be considered as a comorbidity/differential in HK patients
Other infections: Some case reports implicate streptococcal species and various viral agents, but evidence is weak

The striking female predominance suggests a role for oestrogen:
- Oestrogen modulates immune responses (upregulates Th2 pathways, affects B-cell survival and cytokine production)
- However, the exact mechanism by which sex hormones influence TA susceptibility is not fully elucidated
- Pregnancy can both trigger flares and, paradoxically, be well tolerated in some patients with stable disease

Hong Kong Focus

Given the high TB burden in HK relative to other developed cities, the TB-TA connection is particularly relevant. Always screen for latent TB before initiating immunosuppressive therapy for TA. A positive IGRA or tuberculin skin test does not confirm TB as the cause of TA, but latent TB must be treated to prevent reactivation under immunosuppression.

5. Pathophysiology

Understanding the pathophysiology explains every clinical feature.

TA classically progresses through two phases, though they often overlap:

Phase	Pathology	Clinical Correlate
Early (Pre-pulseless / Systemic / Active inflammatory)	Active granulomatous inflammation of vessel wall with oedema; wall thickening on imaging	Constitutional symptoms: fever, fatigue, weight loss, arthralgias, elevated inflammatory markers. Pulses still present. Often misdiagnosed as infection or other rheumatic disease
Late (Pulseless / Occlusive / "Burned-out")	Intimal fibrosis and stenosis ± aneurysm formation; vessel wall scarring	Ischaemic symptoms: claudication, absent pulses, bruits, HTN, stroke, angina. Inflammatory markers may be normal despite ongoing vascular damage

Clinical Pearl: Up to 50% of patients with clinically "inactive" TA (normal ESR/CRP) still have histologically active disease on biopsy. This means you cannot rely on inflammatory markers alone to assess disease activity — serial vascular imaging is essential.

Pathological Process	Mechanism	Clinical Consequence
Stenosis/occlusion of subclavian arteries	Intimal hyperplasia → luminal narrowing	Upper limb claudication, absent radial pulses, asymmetric BP, subclavian steal syndrome
Stenosis of carotid arteries	Reduced cerebral perfusion	Dizziness, syncope, stroke, TIA, visual disturbances
Stenosis of renal arteries	Reduced renal perfusion → activation of RAAS	Renovascular hypertension (most common cause of HTN in TA)
Stenosis of mesenteric arteries	Reduced mesenteric blood flow	Post-prandial abdominal pain (mesenteric angina), weight loss
Stenosis of coronary ostia	Reduced coronary flow	Angina, myocardial infarction
Aortic root dilatation / aneurysm	Destruction of elastic media → wall weakening	Aortic regurgitation (most common valvular lesion in TA), aortic dissection
Stenosis of descending aorta	Mid-aortic syndrome	Lower limb claudication, radio-femoral delay (mimics coarctation)
Pulmonary artery involvement	Stenosis/occlusion of pulmonary arteries	Pulmonary hypertension, dyspnoea, chest pain

6. Classification

TA is classified as a large vessel vasculitis (LVV) under the Chapel Hill Consensus Conference (CHCC) 2012 nomenclature:

Large vessel vasculitis: involving aorta and main branches → Giant cell arteritis, Takayasu arteritis ^[2]^[3]

Category	Examples
Large vessel vasculitis	Giant cell arteritis (GCA), Takayasu arteritis (TA)
Medium vessel vasculitis	Polyarteritis nodosa (PAN), Kawasaki disease
Small vessel vasculitis (ANCA)	GPA, EGPA, MPA
Small vessel vasculitis (Immune complex)	IgA vasculitis (HSP), Cryoglobulinaemic vasculitis
Variable vessel vasculitis	Behçet's disease, Cogan's syndrome

As described in the anatomy section — Types I through V based on distribution. This classification guides surgical/interventional planning.

From the senior notes comparing vasculitis subtypes ^[4]:

Feature	Takayasu Arteritis	Giant Cell Arteritis
Age	< 50 years	≥ 50 years
Sex	F >> M	F > M
Vessels	Aorta + major branches	Temporal, cranial arteries + aorta
Granuloma	Yes	Yes
Renal	Renal artery stenosis (arteritis) → HTN	Rarely
Pulmonary	Can be involved	Extremely rare
Peripheral neuropathy	No	No
GI	Rare (mesenteric ischaemia)	Rare
Skin	Rare	No
Association	—	Polymyalgia rheumatica (40-50%)

7. Clinical Features

TA often presents in two clinical phases, and patients may present in either one (or both concurrently). The early phase is often missed because it is non-specific.

7.1 Symptoms

Constitutional symptoms (40%) ^[1]

Low-grade fever — due to circulating pro-inflammatory cytokines (IL-6, TNF-α) acting on the hypothalamic thermoregulatory centre
Fatigue and malaise — the "sickness behaviour" response mediated by cytokines on the CNS
Weight loss — driven by chronic inflammation (increased metabolic rate, anorexia from cytokines)
Night sweats — febrile response with diurnal cycling
Myalgias and arthralgias — cytokine-mediated musculoskeletal inflammation

Arthralgias (50%) ^[1]

Why is the early phase so often missed? Because these symptoms are entirely non-specific — they mimic infection, malignancy, or any other inflammatory condition. The key clue is the demographic (young Asian female) combined with any vascular symptom.

These are the symptoms that bring patients to attention and are directly explained by which vessels are stenosed or occluded:

1. Upper Limb Claudication

Claudication (70%) ^[1]

Mechanism: Stenosis/occlusion of the subclavian and/or axillary arteries → insufficient blood flow to the upper limb muscles during exertion → anaerobic metabolism → lactic acid accumulation → aching, cramping pain on use, relieved by rest
The arms are more commonly symptomatic than the legs in TA (contrast with atherosclerotic PAD where legs predominate), because the aortic arch branches (subclavian arteries) are preferentially affected
Patients may complain of arm fatigue with overhead activities (e.g., hanging laundry, writing on a board)

2. Dizziness, Syncope, and Visual Disturbances

Mechanism: Stenosis of the common carotid or vertebral arteries → reduced cerebral perfusion, particularly in the posterior circulation
Exacerbated by postural changes or exertion
Can present as pre-syncope, frank syncope, or transient visual blurring

3. Headache

Can be due to carotid/vertebral stenosis with altered cerebral haemodynamics
May also reflect hypertension from renal artery stenosis

4. Angina / Chest Pain

Mechanism: Involvement of the coronary ostia or proximal coronary arteries → myocardial ischaemia
Can also be due to aortic regurgitation (increased myocardial oxygen demand from volume overload)
TA is listed as a cause of non-atherosclerotic coronary artery disease ^[5]

5. Dyspnoea

Multiple mechanisms:
- Aortic regurgitation → volume overload → heart failure
- Pulmonary artery stenosis → pulmonary hypertension
- Myocardial ischaemia → systolic dysfunction

6. Abdominal Pain (Mesenteric Angina)

Mechanism: Stenosis of the coeliac trunk, SMA, or IMA → mesenteric ischaemia → post-prandial abdominal pain (typically 15–30 minutes after eating, "intestinal angina")
Leads to food avoidance and weight loss

Other symptoms: angina, mesenteric ischemia (postprandial angina), stroke/transient neurological symptoms ^[2]

7. Hypertension

This deserves special emphasis because it is the most common complication and a major cause of morbidity

Hypertension (30%) ^[1] — though other sources report > 50% ^[2]

Mechanism: Renal artery stenosis → reduced renal perfusion → activation of the renin-angiotensin-aldosterone system (RAAS) → renovascular hypertension
May also result from decreased aortic compliance (stiff, fibrosed aorta) or coarctation-like narrowing of the mid-aorta
Important: in TA, BP measured in the arms may be falsely low due to subclavian stenosis — always check 4-limb BP to unmask true hypertension

Must-Know Clinical Pearl

A young woman with "normal" BP readings in the arms may actually be severely hypertensive — if both subclavian arteries are stenosed, the arm cuff readings will be falsely low. Always check leg BP (popliteal/ankle) and look for other clues of hypertension (LVH on echo/ECG, hypertensive retinopathy, proteinuria). This is a classic exam trap.

8. Stroke / TIA

Mechanism: Stenosis or occlusion of the carotid or vertebral arteries → thrombotic or haemodynamic ischaemic stroke
TA is listed as a cause of large vessel extracranial ischaemic stroke ^[6]

9. Subclavian Steal Syndrome

Subclavian steal syndrome ^[3]

Mechanism: Severe stenosis/occlusion of the subclavian artery proximal to the origin of the vertebral artery → during arm exercise, blood is "stolen" from the vertebral artery (retrograde flow) to supply the arm → vertebrobasilar insufficiency
Symptoms: dizziness, vertigo, syncope, visual disturbance — all triggered by ipsilateral arm exertion

7.2 Signs

1. Bruits

Bruits (80%) ^[1]

Mechanism: Turbulent blood flow through stenosed arterial segments
Usually audible over subclavian, brachial, carotid, abdominal vessels ^[2]
Auscultate: supraclavicular fossae (subclavian), neck (carotid), epigastrium/flanks (abdominal aorta, renal arteries)

2. Diminished or Absent Pulses

Decreased pulses (60%) ^[1]

Most commonly radial, often asymmetric ^[2]
Mechanism: Stenosis or occlusion of subclavian/axillary/brachial arteries → reduced or absent pulse distally
Check: bilateral radial, ulnar, brachial, carotid, femoral, popliteal, dorsalis pedis, and posterior tibial pulses
This is why it is called "pulseless disease"

3. Asymmetric Blood Pressure

Asymmetric BP (50%) ^[1]

A difference of > 10 mmHg systolic between the two arms is considered significant
May even find unrecordable BP in one or both arms if there is complete occlusion
Always perform 4-limb BP assessment

4. Hypertension Signs

May detect LV heave (from LVH due to chronic hypertension)
Hypertensive retinopathy on fundoscopy (flame haemorrhages, cotton-wool spots, papilloedema)
Takayasu retinopathy: characteristic retinal microaneurysms and arteriovenous anastomoses due to chronic retinal hypoperfusion (Takayasu originally described this)

5. Aortic Regurgitation Murmur

Aortic disease: aneurysm / AR ^[3]

Mechanism: Aortic root dilatation from destruction of the elastic media → dilation of the aortic valve annulus → aortic regurgitation
AR occurs in 20–25% of TA patients
Sign: Early diastolic murmur (decrescendo, blowing) best heard at the left sternal edge with the patient sitting forward and in expiration
In chronic AR: wide pulse pressure, collapsing ("water-hammer") pulse, displaced hyperdynamic apex beat

6. Signs of Heart Failure

If longstanding AR or HTN → dilated LV → LV systolic dysfunction → congestive heart failure
Elevated JVP, bibasal crackles, peripheral oedema, displaced apex

The patient may appear well in the early phase (just tired)
May look cushingoid if on long-term corticosteroids
Erythema nodosum (rare skin manifestation)
Pyoderma gangrenosum (very rare)

Clinical Feature	Frequency	Pathophysiological Basis
Bruits	~80%	Turbulent flow through stenosed segments
Limb claudication	~70%	Arterial stenosis → exertional ischaemia of limb muscles
Absent/weak pulses	~60%	Subclavian/axillary stenosis/occlusion
Arthralgias	~50%	Systemic cytokine-mediated inflammation
Asymmetric BP	~50%	Unilateral or bilateral subclavian stenosis
Hypertension	30–50%+	Renal artery stenosis → RAAS activation; reduced aortic compliance
Constitutional symptoms	~40%	Pro-inflammatory cytokines (IL-6, TNF-α)
Aortic regurgitation	20–25%	Aortic root dilatation → annular dilatation
Neurological symptoms	Variable	Carotid/vertebral stenosis → cerebral hypoperfusion
Angina	Variable	Coronary ostial stenosis; AR-related demand ischaemia
Mesenteric ischaemia	Rare	Coeliac/SMA stenosis → postprandial ischaemia
Stroke/TIA	Variable	Carotid/vertebral occlusion → cerebral infarction
Subclavian steal	Variable	Proximal subclavian occlusion → retrograde vertebral flow
Pulmonary HTN	Variable	Pulmonary artery stenosis

TB screening: Essential before starting immunosuppression — use IGRA (QuantiFERON-TB Gold or T-SPOT.TB) and CXR. Latent TB infection (LTBI) must be treated with isoniazid prophylaxis before or concurrently with corticosteroids/immunosuppressants.
Hepatitis B: HK has a relatively high HBV carrier rate (~7–8% historically). Screen all patients with HBsAg, anti-HBs, anti-HBc, and if positive, check HBV DNA. Immunosuppression can trigger HBV reactivation → antiviral prophylaxis (entecavir or tenofovir) is mandatory.
Atherosclerosis overlap: In older TA patients in HK (especially those with hypertension, DM, dyslipidaemia), atherosclerotic disease may coexist and confound vascular imaging. The key discriminator is the age of onset, pattern of involvement (proximal large vessels in TA vs. diffuse atheromatous disease), and wall thickening on cross-sectional imaging.

High Yield Summary

Definition: Granulomatous large vessel vasculitis of the aorta and its major branches, a.k.a. "pulseless disease" / "aortic arch syndrome" / "occlusive thromboaortopathy"

Epidemiology: Young women (10–40 years), F:M ~8–9:1 in Asians, more common in Asians

Pathophysiology: Granulomatous inflammation of arterial wall (adventitia → media) → two outcomes: (1) intimal hyperplasia/fibrosis → stenosis/occlusion → ischaemia; (2) media destruction → aneurysm/dilatation → AR, rupture risk

Key Clinical Features (exam favourites, from GC lecture slides):

Bruits (80%), Claudication (70%), Decreased pulses (60%), Arthralgias (50%), Asymmetric BP (50%), Constitutional symptoms (40%), Hypertension (30%)

The "pulseless" clue: Young Asian woman with absent radial pulse, arm claudication, unequal BPs, and a bruit = classic Takayasu until proven otherwise

Don't be fooled by "normal" arm BP: Subclavian stenosis gives falsely low arm readings → always do 4-limb BP

Hypertension in TA: Most commonly due to renal artery stenosis → RAAS activation

Investigations: Markers of inflammation + Aortography/MR angiography (GC lecture slides)

Treatment: High dose corticosteroids + Immunosuppressive drugs + Anti-IL6 (GC lecture slides)

Contrast with GCA: TA < 50 years, GCA ≥ 50 years; both are granulomatous large vessel vasculitides

Active Recall - Takayasu Arteritis

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (p89-90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (p96 — Section 3.6.2 Takayasu Arteritis) ^[3] Senior notes: Maksim Medicine Notes.pdf (p332 — Section 13.9 Vasculitis, Takayasu arteritis) ^[4] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1766 — Vasculitis subtypes comparison table) ^[5] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p384-395 — Coronary artery disease, non-atherosclerotic causes) ^[6] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1213 — Causes of ischaemic stroke, large vessel extracranial)

Differential Diagnosis of Takayasu Arteritis

Before we dive into specific differentials, let's frame the clinical challenge. TA typically presents in one of two ways, and the differential diagnosis list differs for each:

Early (pre-pulseless) phase: A young woman with constitutional symptoms (fever, fatigue, weight loss, arthralgias) and raised inflammatory markers — the differential here is wide and includes infections, malignancies, and other inflammatory/autoimmune conditions.
Late (pulseless/occlusive) phase: A young woman with absent pulses, asymmetric BP, bruits, claudication, hypertension, or stroke — the differential here centres on other causes of large vessel stenosis/occlusion or aortic disease.

Additionally, specific presenting features such as unequal BP and pulses, renovascular hypertension in a young person, or unexplained aortitis on imaging each have their own differential.

The key thought process: you need to distinguish TA from conditions that cause (a) large vessel inflammation, (b) large vessel stenosis/occlusion without inflammation, or (c) systemic inflammation with constitutional symptoms.

Detailed Differential Diagnoses

This is the single most important differential for Takayasu arteritis because both are large vessel vasculitides with granulomatous histology affecting the aorta and its branches ^[2]^[3]^[7].

Giant cell arteritis — a granulomatous arteritis of the aorta and its major branches. Commonest form of primary vasculitis. ~20/100,000 person-years. Female:male = 2:1. Predominantly the elderly. ^[7]

Why they look alike:

Both cause stenosis, occlusion, and aneurysm of the aorta and branches
Both show granulomatous inflammation with giant cells on histology
Both present with constitutional symptoms, raised ESR/CRP
GCA can produce an "aortic arch syndrome" with aneurysm, dissection, stenosis of aorta and its major branches (DDx Takayasu's arteritis) ^[3]
Both can cause bruits, asymmetric BP, and absent pulses

How to distinguish them:

Feature	Takayasu Arteritis	Giant Cell Arteritis
Age at onset	< 50 years ^[1]	≥ 50 years (mean ~70y) ^[7]
Sex	F >> M (8–9:1 in Asians)	F > M (2–3:1)
Cranial symptoms	Absent	Temporal headache, scalp tenderness, jaw claudication ^[7]
Visual complications	Rare (retinal hypoperfusion)	Loss of vision (AAION) — sight-threatening emergency ^[7]
PMR association	No	40–50% have PMR ^[3]^[7]
Temporal artery	Normal	Tender, non-pulsatile ^[7]
Temporal artery biopsy	Normal	Diagnostic (giant cells, intimal hyperplasia)
HLA association	HLA-B*52	HLA-DRB1*04
Ethnicity	More common in Asians ^[1]	More common in Northern Europeans

High Yield – GCA vs TA

GCA is a potentially sight-threatening disease and the importance for timely diagnosis and treatment ^[8]. The urgency of distinguishing GCA from TA lies in the risk of irreversible blindness in GCA — if a patient > 50 years presents with large vessel disease + headache or visual symptoms, treat as GCA until proven otherwise (urgent steroids, do NOT wait for biopsy).

Some experts increasingly consider GCA and TA to be a spectrum of the same disease (both granulomatous large vessel vasculitides), differing mainly by age of onset. The 2022 ACR/EULAR classification criteria use age 50 as the dividing line, but overlap cases exist.

Imaging clue for GCA: Urgent Doppler ultrasound of the temporal arteries — circumferential hypoechoic vessel wall thickening around the lumen ("halo sign") and non-compressibility of the temporal artery ^[8]

PET-CT shows circumferential uptake in aortic wall not accountable by localised and minimal atherosclerotic plaque ^[8] — this finding indicates large vessel GCA (or TA if < 50 years) and helps distinguish inflammatory aortitis from atherosclerosis.

Why it can mimic TA:

Both cause limb claudication, absent pulses, bruits, and renovascular hypertension
Atherosclerotic disease can affect the aorta and its branches
Causes of chronic limb ischaemia: Atherosclerosis (most common), Vasculitis e.g. Takayasu arteritis ^[4]^[9]

How to distinguish:

Feature	Takayasu Arteritis	Atherosclerotic PAD
Age	Young (10–40y)	Older (> 50y, typically > 60y)
Sex	F >> M	M > F
Risk factors	No traditional CV risk factors	Smoking, DM, HT, hyperlipidaemia ^[4]
Distribution	Proximal large vessels (aortic arch, subclavian)	Distal vessels (iliac, femoral, popliteal, tibial)
Upper limb involvement	Very common	Rare
Inflammatory markers	↑ESR/CRP	Usually normal
Imaging	Concentric smooth wall thickening	Irregular calcified plaques, eccentric stenosis
Associations	No coronary/cerebrovascular atherosclerosis	Often coexists with IHD, stroke, AAA

Key principle: In a young woman with no cardiovascular risk factors presenting with upper limb claudication and absent radial pulses, atherosclerosis is extremely unlikely. Conversely, in a 70-year-old smoker with lower limb claudication, think atherosclerosis first.

What it is: A non-inflammatory, non-atherosclerotic vascular disease causing arterial stenosis, occlusion, aneurysm, and dissection — predominantly in young to middle-aged women. ^[6]

"Fibro" = fibrous tissue; "muscular" = involving the muscular layer; "dysplasia" = abnormal growth

Why it can mimic TA:

Affects young women
Causes arterial stenosis, renovascular hypertension, bruits
Can affect renal, carotid, and vertebral arteries

How to distinguish:

Feature	Takayasu Arteritis	FMD
Inflammation	↑ESR/CRP, wall thickening	No inflammation, normal ESR/CRP
Aorta involvement	Yes (hallmark)	No (primarily medium-sized arteries)
Imaging pattern	Concentric wall thickening, long-segment stenosis	"String of beads" appearance on angiography
Constitutional symptoms	Present (40%)	Absent
Vessels commonly affected	Aorta, subclavian, carotid	Renal arteries (most common), internal carotid, vertebral
Histology	Granulomatous inflammation	Fibrous/muscular hyperplasia of media

Why it can mimic TA:

Differential diagnosis of unequal BP and pulses: Peripheral artery disease (atherosclerosis, arterial thrombosis), Aortic dissection, Supravalvar aortic stenosis ^[10]^[11] — and by extension, CoA

Both cause upper limb hypertension, radiofemoral delay, absent/weak lower limb pulses
TA itself can cause an "acquired coarctation" (mid-aortic syndrome)
Importantly, TA is listed as an acquired cause of CoA ^[5]

How to distinguish:

Feature	Takayasu Arteritis	Coarctation of Aorta
Age of presentation	10–40y (acquired)	Congenital (neonatal or childhood)
Inflammatory markers	↑ESR/CRP	Normal
Imaging	Diffuse wall thickening, multiple stenoses	Discrete narrowing at aortic isthmus (near ligamentum arteriosum)
Associated findings	Multiple vascular territories involved	Bicuspid aortic valve, Turner syndrome, rib notching on CXR
Upper limb pulses	May be absent (subclavian stenosis)	Strong/bounding (proximal to coarctation)

Why it enters the differential:

Both can present with asymmetric BP, asymmetric pulses, and acute vascular insufficiency
TA itself is a risk factor for aortic dissection (weakened vessel wall) ^[3]
Acute aortic dissection can cause sudden absent pulse, limb ischaemia, or stroke — these can mimic acute-on-chronic TA or be a complication of TA

How to distinguish:

Dissection is acute (sudden onset tearing chest/back pain) vs. TA is chronic/insidious
CT aortogram shows intimal flap with true and false lumen in dissection vs. concentric wall thickening in TA
Dissection is a surgical emergency — do not delay imaging

Why it matters, especially in Hong Kong:

TB aortitis: TB can cause granulomatous inflammation of the aorta and its branches, producing stenosis and aneurysm — histologically indistinguishable from TA without special stains/cultures
- Given the TB–TA epidemiological overlap and the molecular mimicry hypothesis, some cases initially labelled "TA" may actually be TB aortitis
- Always exclude TB with IGRA, sputum for AFB, and tissue cultures when available
Syphilitic aortitis: Tertiary syphilis causes inflammation of the vasa vasorum ("endarteritis obliterans of the vasa vasorum") → destruction of the aortic media → aneurysm (classically ascending aorta), aortic regurgitation, coronary ostial stenosis
- Screen with RPR/VDRL and confirmatory TPHA/FTA-ABS
- Less common today but still relevant in HK

Feature	Takayasu Arteritis	TB Aortitis	Syphilitic Aortitis
Age/sex	Young female	Any age	Middle-aged/elderly
Histology	Granulomatous (non-caseating)	Granulomatous (caseating) with AFB	Endarteritis obliterans of vasa vasorum, plasma cell infiltrate
Site	Aortic arch + abdominal aorta	Variable	Ascending aorta (classically)
Constitutional S/S	Yes	Yes (± pulmonary TB)	No (late/tertiary stage)
Specific tests	Clinical + imaging	IGRA, AFB, tissue culture, PCR	RPR/VDRL, TPHA

What it is: An immune-mediated fibroinflammatory condition that can affect virtually any organ. When it involves the aorta, it causes IgG4-related aortitis/periaortitis — presenting as aortic wall thickening, aneurysm, or retroperitoneal fibrosis.

Why it can mimic TA:

Aortic wall thickening on imaging
Can cause stenosis of aortic branches
Elevated inflammatory markers

How to distinguish:

Serum IgG4 level is typically elevated (though not always)
Histology shows dense lymphoplasmacytic infiltrate with storiform fibrosis and obliterative phlebitis (distinct from granulomatous inflammation of TA)
Often involves other organs simultaneously: pancreas (autoimmune pancreatitis), salivary/lacrimal glands, retroperitoneum, kidneys
Responds dramatically to corticosteroids (like TA), but histology is the differentiator

Why it enters the differential:

Variable vessel vasculitis that can affect arteries and veins of any size
Can cause arterial stenosis, aneurysm, and thrombosis of large vessels
More common in the "Silk Road" belt (Turkey, Iran, East Asia including China/HK)
Young adults, slight male predominance

How to distinguish:

Behçet's has characteristic mucocutaneous features: recurrent oral and/or genital aphthous ulcers, cutaneous lesions, ocular inflammatory lesions ^[12]
Venous involvement (DVT, cerebral venous sinus thrombosis) is common in Behçet's but rare in TA
Pathergy test (skin hyperreactivity) is positive in many Behçet's patients
No granulomatous histology — predominantly neutrophilic inflammation

A medium vessel necrotizing vasculitis ^[13]
Can cause renovascular hypertension, mesenteric ischaemia, and renal infarctions — superficially resembling TA
However, PAN does not affect the aorta itself — it targets medium-sized muscular arteries (renal, mesenteric, hepatic)
Key differentiators: mononeuritis multiplex (up to 70% in PAN, absent in TA), skin lesions (livedo reticularis, nodules, purpura), microaneurysms on angiography, ANCA usually negative, association with HBV ^[13]
PAN has no pulmonary involvement and no glomerulonephritis

Affects small and medium vessels of hands and feet — not the aorta ^[4]
Young male smokers (30–40s)
Causes digital ischaemia, rest pain, ulcers, gangrene, superficial thrombophlebitis, Raynaud's phenomenon
Distinguished from TA by: exclusively distal vessel involvement, strong smoking association, no aortic involvement, "corkscrew" collaterals on angiography

Condition	Key Distinguishing Features
Mid-aortic syndrome (MAS)	Segmental narrowing of abdominal aorta; can be congenital, secondary to NF1, or due to TA itself
Neurofibromatosis type 1 (NF1)	Renal artery stenosis, coarctation, moyamoya — look for café-au-lait spots, neurofibromas
Ehlers-Danlos syndrome (vascular type IV)	Arterial rupture/dissection rather than stenosis; translucent skin, easy bruising, family history
Marfan syndrome	Aortic root dilatation/dissection; tall, arm span > height, lens subluxation, pectus excavatum
Radiation arteritis	History of prior thoracic/mediastinal radiation; affects vessels in radiation field only
Ergotism	Vasospasm from ergot alkaloids; severe limb ischaemia, can cause absent pulses but reversible on drug withdrawal
Thrombotic conditions (APS, PV)	Cause arterial thrombosis and occlusion but no wall thickening or inflammation on imaging

Differential	Vessel Size	Age	Sex	Inflammation	Unique Feature
GCA	Large	≥ 50y	F > M	Yes (granulomatous)	Temporal headache, jaw claudication, AAION, PMR
Atherosclerotic PAD	Large–medium	> 50y	M > F	No	CV risk factors, calcified plaques, distal > proximal
FMD	Medium	20–50y	F >> M	No	"String of beads", renal/carotid arteries
CoA	Large (aorta)	Congenital	M > F	No	Discrete isthmus narrowing, rib notching, bicuspid AV
Aortic dissection	Large	Any	M > F	No	Acute tearing pain, intimal flap
TB aortitis	Large	Any	=	Yes (caseating granuloma)	AFB+, caseation, pulmonary TB
Syphilitic aortitis	Large (ascending)	Middle–old	M > F	Yes (vasa vasorum)	Tertiary syphilis, ascending aortic aneurysm
IgG4-RD	Large (peri-aortic)	Middle–old	M > F	Yes (lymphoplasmacytic)	↑serum IgG4, storiform fibrosis, multiorgan
Behçet's	Variable	Young	M > F	Yes (neutrophilic)	Oral/genital ulcers, pathergy, venous thrombosis
PAN	Medium	Middle-aged	M > F	Yes (necrotizing)	Mononeuritis multiplex, micro-aneurysms, HBV, no aorta
Buerger's	Small–medium	Young	M >> F	Yes (thrombotic)	Smokers, distal vessels only, corkscrew collaterals

Exam Pearls for Differential Diagnosis

TA vs GCA: The single differentiator is age (< 50 vs ≥ 50). Both are granulomatous, both affect the aorta. GCA has cranial symptoms (headache, jaw claudication, visual loss) and PMR; TA does not.
TA vs atherosclerosis: TA is a young woman with no CV risk factors and upper limb involvement; atherosclerosis is an older patient with CV risk factors and lower limb predominance.
TA vs FMD: Both affect young women. FMD has no inflammation (normal ESR/CRP) and shows "string of beads" on angiography. FMD does not involve the aorta.
Always exclude TB before starting immunosuppression for TA in Hong Kong — IGRA + CXR at minimum.
If an exam question asks for the DDx of unequal BP and pulses: Peripheral artery disease (atherosclerosis, arterial thrombosis), Aortic dissection, Supravalvar aortic stenosis ^[10]^[11] — and add TA.

Active Recall - Differential Diagnosis of Takayasu Arteritis

References

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (p89–90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (p96 — Section 3.6.2 Takayasu Arteritis) ^[3] Senior notes: Maksim Medicine Notes.pdf (p311, p332 — Vasculitis and GCA sections) ^[4] Senior notes: Ryan Ho Cardiology.pdf (p212 — Chronic Limb Ischaemia) ^[5] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p573 — Coarctation of Aorta, acquired causes) ^[6] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1213 — Causes of ischaemic stroke, FMD) ^[7] Lecture slides: GC 053. Fingers turn white and blue.pdf (p87 — Giant cell arteritis) ^[8] Lecture slides: GC_Interactive tutorial (Rheum case 1) student copy.pdf (p1, p6 — GCA diagnosis and imaging) ^[9] Senior notes: Maksim Surgery Notes.pdf (p166 — Chronic limb ischaemia) ^[10] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p575 — CoA differential diagnosis) ^[11] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p262 — CoA differential diagnosis) ^[12] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1765 — Behçet's syndrome definition) ^[13] Senior notes: Ryan Ho Rheumatology.pdf (p159 — Polyarteritis Nodosa)

Diagnostic Criteria, Algorithm, and Investigations for Takayasu Arteritis

1. Diagnostic Criteria

There is no single "gold standard" diagnostic test for Takayasu arteritis. Diagnosis is based on the combination of clinical features + compatible vascular imaging, supported by laboratory evidence of inflammation and exclusion of mimics ^[2]. Two major sets of classification criteria exist:

The American College of Rheumatology (ACR) published classification criteria in 1990. These were designed to classify patients for research purposes (i.e., to distinguish TA from other vasculitides once a diagnosis of vasculitis has been established), not strictly for diagnosis in clinical practice. However, they are widely used and commonly tested in exams.

≥ 3 of 6 criteria → classifies as TA (sensitivity 90.5%, specificity 97.8%)

#	Criterion	Rationale
1	Age at disease onset ≤ 40 years	Reflects the typical young demographic; distinguishes from GCA (≥ 50y) and atherosclerosis
2	Claudication of extremities	Limb ischaemia from stenosis of major branches of the aorta
3	Decreased brachial artery pulse	Subclavian/axillary stenosis → diminished or absent radial/brachial pulse
4	BP difference > 10 mmHg between arms	Asymmetric subclavian stenosis creates a pressure gradient
5	Bruit over subclavian arteries or aorta	Turbulent flow through stenosed segments
6	Arteriographic abnormality	Narrowing or occlusion of the entire aorta, its primary branches, or large arteries in the proximal upper or lower extremities, not due to atherosclerosis, fibromuscular dysplasia, or similar causes

Important: Classification vs Diagnosis

The ACR 1990 criteria are classification criteria — they assume a patient has already been identified as having vasculitis. They are not diagnostic criteria for a first-time clinical assessment. In clinical practice, many TA patients in the early (pre-pulseless) phase would NOT meet 3/6 criteria because they may only have constitutional symptoms and raised inflammatory markers without yet having developed stenosis, absent pulses, or bruits. Always consider TA in a young woman with unexplained constitutional symptoms and raised ESR/CRP even if ACR criteria are not yet met.

Mnemonic for ACR criteria — "ABCABC":

Age ≤ 40

Brachial pulse decreased

Claudication of extremities

Arteriographic abnormality

BP difference > 10 mmHg

Carotid/subclavian/aortic bruit

The 2022 ACR/EULAR criteria represent the most current evidence-based classification system. They apply only to patients in whom a diagnosis of medium- or large-vessel vasculitis has already been established.

Required entry criterion: Diagnosis of medium- or large-vessel vasculitis (based on clinical assessment and imaging/biopsy)

Then apply a weighted scoring system — a score of ≥ 5 points classifies as TA:

Criterion	Points
Age at onset ≤ 60 years	+1
Female sex	+1
Angina or ischaemic cardiac pain	+2
Arm or leg claudication	+2
Arterial bruit	+2
Reduced pulse in upper extremity	+2
Carotid artery involvement on imaging	+2
Number of affected arterial territories ≥ 1 (abdominal aorta + renal, or other territories)	+1 per territory (max +3)
Paired temporal artery abnormality on biopsy or imaging	−5 (i.e., makes GCA more likely, penalises TA classification)

Key innovations:

Age cut-off raised to ≤ 60 (acknowledging overlap cases)
Explicitly penalises temporal artery involvement (which favours GCA)
Weighted scoring reflects relative importance of features
Imaging features are formally incorporated

While less commonly used today, Ishikawa proposed clinical diagnostic criteria requiring the obligatory criterion (age ≤ 40 years) plus 2 major or 1 major + 2 minor or 4 minor criteria. Major criteria included features like mid-aortic lesion and descending aortic lesion on imaging. These have been largely superseded by the ACR and ACR/EULAR systems.

The practical clinical approach to diagnosing TA follows a systematic pathway from clinical suspicion through investigation to confirmed diagnosis.

Practical Approach — The 3 Pillars of TA Diagnosis

Clinical features: Compatible demographics (young woman) + vascular signs (absent pulses, bruits, asymmetric BP, claudication, HTN) ± constitutional symptoms
Vascular imaging: Demonstrating wall thickening, stenosis/occlusion, or aneurysm of the aorta and/or its major branches in a typical distribution — Investigations: Markers of inflammation, Aortography, MR angiography ^[1]
Exclusion of mimics: Atherosclerosis, FMD, CoA, infectious aortitis (TB, syphilis), IgG4-RD, connective tissue disorders (Marfan, EDS)

Ix: dx based on clinical finding + vascular imaging ^[2]

3. Investigations: Modalities, Key Findings, and Interpretation

A. Blood Tests (Laboratory Investigations)

Investigations: Markers of inflammation ^[1]

Test	Expected Finding	Interpretation and Rationale
ESR	↑ (often > 40 mm/h, can be > 100)	Non-specific marker of systemic inflammation. Reflects increased acute-phase proteins (mainly fibrinogen) causing rouleaux formation of RBCs and faster sedimentation. Elevated in active TA but can be normal in up to 30-40% of patients with active disease — this is a crucial pitfall
CRP	↑	Hepatic acute-phase protein produced in response to IL-6. More rapidly responsive than ESR. Also can be normal despite active vessel wall inflammation

ESR/CRP Limitation — Exam Must-Know

A normal ESR and CRP do NOT exclude active Takayasu arteritis. Studies show that up to 30–40% of patients with clinically and histologically active disease have normal inflammatory markers. This is why serial vascular imaging is mandatory for disease monitoring, not inflammatory markers alone. Conversely, a persistently elevated ESR/CRP in a treated patient should raise suspicion for disease relapse (or alternative causes like intercurrent infection).

Test	Expected Finding	Interpretation
Haemoglobin	Normochromic normocytic anaemia	Anaemia of chronic disease — hepcidin-mediated iron sequestration due to IL-6; reduced RBC survival
WBC	Normal or mild leukocytosis	Non-specific inflammatory response
Platelets	Reactive thrombocytosis	IL-6 stimulates thrombopoietin production → ↑megakaryopoiesis

Test	Rationale
RFT (urea, creatinine, eGFR)	Assess for renal impairment from renal artery stenosis
Urinalysis (protein, blood)	Hypertensive nephropathy or rarely renal vasculitis
LFT	Baseline before immunosuppressive therapy; also TA can rarely cause hepatic artery stenosis
Fasting glucose, HbA1c	Baseline before starting corticosteroids (steroid-induced hyperglycaemia)
Lipid profile	Assess cardiovascular risk and exclude atherosclerosis as primary cause

Test	Rationale
IGRA (QuantiFERON-TB Gold / T-SPOT.TB)	Screen for latent TB — mandatory before immunosuppression in HK; also to exclude TB aortitis as the underlying cause
RPR/VDRL ± TPHA/FTA-ABS	Exclude syphilitic aortitis
HBsAg, anti-HBs, anti-HBc, HBV DNA	Screen for HBV (relevant in HK; HBV reactivation risk with immunosuppression; also PAN is HBV-associated)
Anti-HCV	Exclude HCV-related vasculitis and cryoglobulinaemia
ANA, anti-dsDNA	Exclude SLE-associated large vessel vasculitis
ANCA (c-ANCA/PR3, p-ANCA/MPO)	Exclude ANCA-associated vasculitis (GPA/MPA/EGPA) — these are negative in TA
Serum IgG4	Exclude IgG4-related aortitis

Key point: There is no specific serological marker for Takayasu arteritis. ANCA is negative. ANA is negative. RF is negative. The diagnosis rests on clinical features + imaging.

B. Vascular Imaging — The Cornerstone of Diagnosis

Imaging serves three critical purposes in TA:

Diagnosis: Demonstrate vessel wall inflammation and/or structural abnormalities
Disease mapping: Determine the anatomical extent and type (Numano classification)
Disease monitoring: Assess treatment response, detect relapse, guide revascularisation

Investigations: Aortography, MR angiography ^[1]

Vascular imaging: MRA/CTA ^[2]

The most commonly used first-line imaging modality in current practice.

Aspect	Detail
Principle	IV contrast-enhanced CT with arterial phase timing; reconstructs the entire aorta and its branches in thin slices
Key findings in TA	(1) Concentric mural thickening — hallmark finding, typically smooth and homogeneous (cf. irregular calcified plaques in atherosclerosis). (2) Mural enhancement — on delayed-phase imaging, the thickened wall may enhance, suggesting active inflammation. (3) Stenosis/occlusion — luminal narrowing of affected segments. (4) Aneurysm/dilatation — particularly of thoracic or abdominal aorta. (5) Calcification — may be seen in chronic/burned-out disease
Advantages	Widely available; fast; excellent spatial resolution; good for calcification detection; can assess entire aorta + branches in one scan
Limitations	Ionising radiation (important given young patients needing serial imaging); iodinated contrast (allergy, nephrotoxicity); cannot reliably distinguish active inflammation from fibrosis

Preferred for serial monitoring in young patients due to lack of ionising radiation.

Aspect	Detail
Principle	Gadolinium-enhanced or non-contrast (time-of-flight, phase-contrast) MRI sequences
Key findings in TA	(1) Mural thickening with T2 hyperintensity and/or mural enhancement — T2 bright signal and late gadolinium enhancement in the vessel wall suggest active inflammation (oedema). This is a key advantage over CTA. (2) Stenosis/occlusion — demonstrated on contrast-enhanced MRA sequences. (3) Aneurysm — well visualised
Advantages	No ionising radiation — ideal for repeated imaging in young women of reproductive age; can detect mural oedema (active inflammation) using T2-weighted and post-contrast sequences; good soft tissue contrast
Limitations	Longer scan time; less widely available; tends to overestimate stenosis; gadolinium contraindicated in severe renal impairment (risk of nephrogenic systemic fibrosis); inaccurate in stented segments due to metal artefact; poor for detecting calcification

CTA vs MRA — Practical Choice

First presentation / diagnostic workup: CTA (faster, widely available, good anatomical detail)
Serial monitoring / follow-up: MRA (no radiation, can assess wall oedema/activity)
Pregnancy: MRA without gadolinium (use time-of-flight sequences) or Doppler ultrasound

Investigations: Aortography ^[1]

Aspect	Detail
Principle	Catheter inserted (usually via femoral artery) into the aorta; radio-opaque contrast injected and real-time X-ray fluoroscopy captures the arterial lumen
Key findings	(1) Luminal irregularities — stenosis, occlusion, post-stenotic dilatation. (2) "Rat-tail" tapering — smooth, tapered narrowing typical of inflammatory stenosis (cf. irregular "shouldered" stenosis in atherosclerosis). (3) Aneurysm. (4) Collateral vessel formation — around occluded segments
Historical significance	Was the gold standard (referenced in ACR 1990 criteria as "arteriographic abnormality")
Current role	Only when surgery/intervention is planned ^[14] — has been largely replaced by CTA/MRA for diagnostic purposes because it is invasive and only shows the lumen (cannot assess wall thickening, which is the early sign of TA). Used intraoperatively to guide endovascular intervention
Limitations	Invasive; only shows lumen (not wall); iodinated contrast; risks include dissection, embolism, pseudoaneurysm, contrast nephropathy

Vasculitis investigations: biopsy if tissue accessible, angiography if tissue inaccessible ^[3]

This principle is directly applicable to TA — the aorta is not easily biopsied (tissue inaccessible), so angiography (now CTA/MRA) is the primary diagnostic approach.

Aspect	Detail
Principle	18F-fluorodeoxyglucose (FDG) is taken up by metabolically active cells, including activated macrophages and T lymphocytes in inflamed vessel walls. Combined with CT for anatomical localisation
Key findings	Circumferential FDG uptake in the aortic wall and/or its branches — indicates active vascular inflammation
Advantages	Excellent for detecting active inflammation even before structural changes develop (i.e., in the early pre-pulseless phase); can assess the entire vascular tree in one scan; helps distinguish active inflammation from chronic fibrotic/"burned-out" disease
Limitations	Expensive; not widely available; radiation exposure; false positives in atherosclerotic plaques (though pattern of uptake differs — TA shows smooth, circumferential uptake vs. focal/patchy uptake in atherosclerosis); sensitivity decreases after corticosteroid treatment (steroids suppress macrophage activity, reducing FDG uptake)

PET-CT shows circumferential uptake in aortic wall not accountable by localised and minimal atherosclerotic plaque ^[15] — this GC lecture slide finding is a classic description of active large vessel vasculitis on PET-CT, distinguishing it from the patchy uptake seen in atherosclerosis.

PET-CT in Large Vessel Vasculitis — High Yield from GC Tutorial

Investigations for GCA, especially the role of imaging for GCA diagnosis ^[15] — PET-CT is increasingly used for both GCA and TA to:

Detect active large vessel inflammation
Map the extent of vascular involvement
Monitor treatment response

The pattern is key: circumferential uptake in the aortic wall = vasculitis. Focal/patchy uptake = atherosclerosis. This principle applies equally to TA and GCA with extra-cranial large vessel involvement.

Aspect	Detail
Principle	B-mode imaging + Doppler flow assessment of accessible arteries (carotid, subclavian, axillary, vertebral, femoral, renal)
Key findings	(1) "Macaroni sign" — diffuse, homogeneous, concentric, hypoechoic wall thickening of the common carotid artery, resembling a macaroni noodle in cross-section. This is the TA equivalent of the "halo sign" in GCA. (2) Increased peak systolic velocity — at stenotic segments. (3) Absent/reversed flow — in occluded vessels or subclavian steal
Advantages	Non-invasive, no radiation, no contrast, cheap, bedside, repeatable; good for superficial vessels
Limitations	Operator-dependent; cannot assess thoracic/abdominal aorta well (limited by body habitus, bowel gas); poor for deep/central vessels

Compare with the GCA finding on ultrasound: circumferential hypoechoic vessel wall thickening around the lumen of the temporal artery, not compressible ^[15] — this "halo sign" principle is identical in concept to the "macaroni sign" in TA, just in different vessels.

Aspect	Detail
Indication	All TA patients should have a baseline echocardiogram to assess for cardiac complications
Key findings	(1) Aortic regurgitation — from aortic root dilatation (the most common valvular lesion in TA). (2) LV hypertrophy — from chronic hypertension. (3) LV dilatation and systolic dysfunction — in advanced disease with heart failure. (4) Aortic root dilatation — direct evidence of aortitis. (5) Pulmonary hypertension — if pulmonary arteries are involved

± histopathology: seldom done ^[2]

Aspect	Detail
When obtained	Rarely — only when surgical specimens are available (e.g., during bypass grafting or aortic repair). Percutaneous biopsy of the aorta is NOT performed
Classic histological findings	(1) Granulomatous inflammation — collections of epithelioid macrophages and multinucleated giant cells (Langhans type), predominantly in the media and adventitia. (2) Destruction of the elastic lamina — fragmentation of elastic fibres on elastic van Gieson staining. (3) Intimal fibroplasia — smooth muscle cell proliferation and fibrosis causing luminal narrowing. (4) Adventitial fibrosis — in chronic/burned-out disease. (5) Neovascularisation of the media ("vasa vasorum proliferation")
Differential stains	Ziehl-Neelsen (ZN) stain to exclude TB (caseating granulomas with acid-fast bacilli); PAS/GMS to exclude fungal infection

Modality	What It Shows	Role in TA	Advantages	Limitations
ESR/CRP	Systemic inflammation	Screening, activity monitoring	Cheap, widely available	Normal in 30-40% active disease
CTA	Wall thickening, stenosis, aneurysm, calcification	First-line diagnostic imaging	Fast, widely available, excellent spatial resolution	Radiation, contrast, cannot reliably assess activity
MRA	Wall thickening, oedema (T2), stenosis, aneurysm	Preferred for serial monitoring	No radiation, can detect active wall oedema	Overestimates stenosis, longer scan, gadolinium CI in renal impairment
PET-CT	Active metabolic inflammation in vessel wall	Best for detecting active inflammation	Detects early/pre-structural disease, whole-body	Expensive, radiation, ↓sensitivity on steroids
Doppler USG	Wall thickening, flow abnormalities in superficial arteries	Screening, follow-up of accessible vessels	Non-invasive, cheap, bedside, repeatable	Operator-dependent, cannot assess deep/central vessels
Conventional angiography	Luminal stenosis, occlusion, aneurysm, collaterals	Only for planned intervention	Gold standard for luminal detail, allows concurrent intervention	Invasive, cannot see wall, contrast risks
Echocardiography	AR, LV function, aortic root, pulmonary HTN	Baseline cardiac assessment in all patients	Non-invasive, widely available	Limited to cardiac structures
Histopathology	Granulomatous inflammation, elastic lamina destruction	Confirmatory if tissue available	Definitive	Rarely available (surgical specimens only)

This is one of the most difficult clinical problems in TA management. Unlike many inflammatory diseases, there is no single reliable marker of disease activity.

Current approach uses a combination of:

Domain	Method
Clinical	NIH criteria (1994): new or worsening constitutional symptoms, new vascular findings (bruits, pulse changes, BP changes), ischaemic symptoms
Laboratory	ESR/CRP — but unreliable in isolation
Imaging	MRA (mural oedema on T2/post-contrast) or PET-CT (FDG uptake) — most objective assessment of wall inflammation

The Indian Takayasu Clinical Activity Score (ITAS) and its extension ITAS-A (incorporating ESR/CRP) are validated composite tools used in clinical trials and some centres.

Bottom line for exams: Diagnosis = clinical + imaging. Activity monitoring requires repeated imaging (MRA or PET-CT), not ESR/CRP alone.

High Yield Summary — Diagnosis of Takayasu Arteritis

ACR 1990 Criteria: ≥ 3 of 6 (Age ≤ 40, Claudication, ↓Brachial pulse, BP difference > 10 mmHg, Bruit, Arteriographic abnormality) — mnemonic "ABCABC"

Key investigations from GC lecture slides: Markers of inflammation + Aortography + MR angiography ^[1]

Diagnosis rests on: Clinical features + vascular imaging (CTA or MRA) + exclusion of mimics

No specific serological marker exists — ANCA negative, ANA negative

CTA = first-line diagnostic; MRA = preferred for serial monitoring (no radiation); PET-CT = best for detecting active wall inflammation

Normal ESR/CRP does NOT exclude active TA — up to 40% of patients with active disease have normal inflammatory markers

Always exclude: TB (IGRA), syphilis (RPR), HBV (serology), atherosclerosis, FMD, IgG4-RD before confirming TA

Histopathology: Granulomatous inflammation with giant cells, elastic lamina destruction — rarely obtained (surgical specimens only)

Active Recall - Diagnosis of Takayasu Arteritis

References

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (p89–90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (p96 — Section 3.6.2 Takayasu Arteritis) ^[3] Senior notes: Maksim Medicine Notes.pdf (p332 — Section 13.9 Vasculitis) ^[4] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1766 — Vasculitis subtypes comparison table) ^[14] Senior notes: Maksim Surgery Notes.pdf (p165 — Investigations for PVD) ^[15] Lecture slides: GC_Interactive tutorial (Rheum case 1) student copy.pdf (p1, p4, p6 — GCA diagnosis and imaging)

Management of Takayasu Arteritis

The management of Takayasu arteritis rests on three pillars, each addressing a different aspect of the disease:

Immunosuppressive therapy — to suppress the granulomatous inflammatory process driving vessel wall damage
Vascular/surgical intervention — to address the structural consequences of inflammation (stenosis, occlusion, aneurysm)
Adjunctive/supportive care — to manage complications (hypertension, cardiovascular risk) and prevent treatment-related adverse effects

The guiding principle: you must control the inflammation first (medical therapy) before considering any revascularisation. Operating on an actively inflamed vessel leads to anastomotic complications (restenosis, pseudoaneurysm). Think of it like this — you wouldn't plaster a wall that's still on fire.

1. Immunosuppressive Therapy (Medical Management)

The rationale for immunosuppression: TA is driven by a T-cell and macrophage-mediated granulomatous inflammatory response. The inflammatory cytokine milieu (IL-6, TNF-α, IFN-γ, IL-17) causes progressive vessel wall destruction. Suppressing this immune response halts disease progression and allows vascular healing, preventing further stenosis and aneurysm formation.

Treatment: High dose corticosteroids ^[1]

High-dose corticosteroids: 1 mg/kg/d up to 2–4w then taper ^[2]

Management: high dose steroids + steroid-sparing agents (MTX/AZA) ^[3]

Aspect	Detail
Drug	Prednisolone (oral) or Methylprednisolone (IV for severe/critical presentations)
Dose	1 mg/kg/day (max 60 mg/day) for 2–4 weeks ^[2]
Mechanism	Corticosteroids work at multiple levels: (1) Bind intracellular glucocorticoid receptors → translocate to nucleus → suppress transcription of pro-inflammatory genes (NF-κB, AP-1). (2) Inhibit T-cell activation and proliferation. (3) Reduce macrophage cytokine production (IL-1, IL-6, TNF-α). (4) Suppress adhesion molecule expression → reduce leukocyte migration into vessel wall. Net effect: rapidly dampens the granulomatous inflammation
Response	~60% of patients achieve remission with corticosteroids alone, but relapse is extremely common (50–70%) upon dose reduction
IV pulse steroid	Methylprednisolone 500–1000 mg IV daily for 3 days → then switch to oral prednisolone. Reserved for severe/life-threatening presentations (e.g., critical limb ischaemia, stroke, rapidly progressive visual loss, critical organ ischaemia)

Steroid Taper Protocol:

After 2–4 weeks at full dose, begin a slow taper
Typical approach: reduce by 5–10 mg every 2–4 weeks until reaching 15–20 mg/day, then reduce by 2.5 mg every 2–4 weeks, then by 1 mg every 4 weeks below 10 mg/day
Total taper duration: 12–24 months (often longer)
Guided by clinical status, ESR/CRP, and serial imaging (MRA or PET-CT)
Many patients require a low maintenance dose (5–10 mg/day) for years

Why the Steroid Taper Is So Difficult in TA

TA has an extremely high relapse rate (50–70%) during steroid tapering. This is because corticosteroids suppress the downstream inflammatory response but do not eliminate the underlying immunological drive (likely persistent autoantigen presentation by adventitial dendritic cells). The moment you reduce the dose below a critical threshold, the smouldering immune process reactivates. This is why early introduction of a steroid-sparing agent is essential — it provides a second immunosuppressive mechanism that allows successful steroid taper.

B. Steroid-Sparing Agents (Conventional Immunosuppressants)

Treatment: Immunosuppressive drugs ^[1]

Steroid-sparing agents: usu methotrexate or azathioprine ^[2]

Why use steroid-sparing agents?

To allow steroid dose reduction → minimising long-term steroid side effects (osteoporosis, DM, Cushing syndrome, infections, cataracts, AVN, growth retardation in young patients)
To maintain remission during steroid taper
To treat steroid-refractory or frequently relapsing disease

Aspect	Detail
Drug class	Folate antagonist (at low dose: immunomodulator rather than cytotoxic)
Dose	15–25 mg once weekly (oral or subcutaneous)
Mechanism	At low/immunomodulatory doses: inhibits AICAR transformylase → accumulation of adenosine → adenosine is anti-inflammatory (suppresses T-cell activation, reduces TNF-α and IL-6 production). Also inhibits dihydrofolate reductase → reduces lymphocyte proliferation
Evidence	Open-label studies show ~50% remission rate; allows steroid reduction
Key side effects	Hepatotoxicity, myelosuppression (pancytopenia), pneumonitis, mucositis, teratogenicity
Monitoring	FBC, LFT every 4–8 weeks; CXR baseline
Contraindications	Pregnancy (teratogenic — must use effective contraception; stop 3 months before conception for females, 6 months for males), significant liver disease, severe renal impairment (GFR < 30), active infection, pre-existing cytopenia
Mandatory co-prescription	Folic acid 5 mg weekly (on a different day to MTX) — to reduce folate-deficiency side effects (mucositis, cytopenias) without reducing efficacy

Aspect	Detail
Drug class	Purine analogue prodrug
Dose	2–2.5 mg/kg/day (oral)
Mechanism	Metabolised to 6-mercaptopurine (6-MP) → converted to thiopurine nucleotides → incorporated into DNA → inhibit purine synthesis → suppress lymphocyte proliferation (B and T cells)
Evidence	Similar efficacy to MTX; commonly used as first-line alternative
Key side effects	Myelosuppression (dose-related), hepatotoxicity, GI upset, pancreatitis, increased infection risk, small increased risk of lymphoma with long-term use
Pre-treatment screening	TPMT (thiopurine methyltransferase) activity — TPMT metabolises 6-MP; patients with low/absent TPMT activity accumulate toxic metabolites → severe myelosuppression. Check TPMT genotype/phenotype before starting AZA. Heterozygous = use half dose; homozygous deficient = do NOT use AZA
Monitoring	FBC, LFT every 4–8 weeks
Contraindications	TPMT deficiency, pregnancy (relatively — can be used in pregnancy if benefits outweigh risks, unlike MTX), active infection

Choosing between MTX and AZA: Both are reasonable first-line options. MTX is often preferred in practice due to once-weekly dosing and perhaps slightly stronger evidence, but AZA is preferred in patients of reproductive age who may become pregnant (AZA is considered relatively safer in pregnancy than MTX, which is absolutely contraindicated).

C. Biologic Therapy — Second-Line / Refractory Disease

Treatment: Anti-IL6 ^[1]

Aspect	Detail
Drug class	Humanised monoclonal antibody against the IL-6 receptor
Name breakdown	"Toci" = truncated from "tocilizumab"; "-cizumab" = humanised monoclonal antibody
Dose	162 mg SC weekly or 8 mg/kg IV every 4 weeks
Mechanism	Blocks IL-6 signalling. Why is IL-6 important in TA? IL-6 is a master cytokine in TA pathogenesis: (1) Drives T-cell differentiation (Th17 pathway). (2) Stimulates hepatic acute-phase response (↑CRP, ↑fibrinogen, ↑hepcidin → anaemia). (3) Promotes B-cell differentiation and antibody production. (4) Drives constitutional symptoms (fever, fatigue). By blocking IL-6, tocilizumab suppresses both the systemic inflammatory response and the local granulomatous process in the vessel wall
Evidence	The TAKT trial (2022) showed significantly higher sustained remission rates with tocilizumab vs placebo in relapsing TA. Now recommended by EULAR/ACR for relapsing or refractory TA
Key side effects	Increased infection risk (especially lower respiratory tract), GI perforation (especially with concurrent corticosteroids and diverticular disease), hyperlipidaemia, neutropenia, hepatotoxicity, injection site reactions
Important caveat	Tocilizumab suppresses CRP (because CRP production is IL-6 dependent). This means CRP becomes unreliable for disease monitoring while on tocilizumab — must rely on imaging (MRA/PET-CT) and clinical assessment instead
Contraindications	Active infection (especially TB — screen with IGRA before starting), diverticulitis, significant hepatic impairment, neutropenia

GC Lecture Slide — Anti-IL6 for TA

Anti-IL6 is explicitly listed on the GC lecture slide as a treatment for Takayasu arteritis ^[1]. For exam purposes, know that tocilizumab is the anti-IL-6 receptor antibody used for TA (and GCA). It is used as a steroid-sparing agent in relapsing/refractory disease, not as first-line monotherapy.

For comparison, in GCA: Steroid-sparing agents: tocilizumab (anti-IL6), methotrexate upon relapsing disease ^[16]. The same agents work for both large vessel vasculitides because the pathophysiology (IL-6-driven granulomatous inflammation) is shared.

Agent	Class	Mechanism	Evidence in TA
TNF-α inhibitors (infliximab, etanercept, adalimumab)	Anti-TNF monoclonal antibodies/receptor fusion proteins	Block TNF-α → reduce macrophage activation, granuloma formation, and pro-inflammatory cascading	Case series and small studies show benefit in refractory TA; not formally approved; use considered off-label in steroid/tocilizumab-refractory cases
Mycophenolate mofetil (MMF)	Inosine monophosphate dehydrogenase (IMPDH) inhibitor	Selectively inhibits purine synthesis in lymphocytes → suppresses T and B cell proliferation	Alternative steroid-sparing agent; used in some centres when MTX/AZA fail or are not tolerated
Cyclophosphamide (CYC)	Alkylating agent	Cross-links DNA → kills rapidly dividing cells including lymphocytes	Reserved for severe, life-threatening, or refractory TA only; significant toxicity (myelosuppression, haemorrhagic cystitis, infertility, malignancy risk). Used as induction in critical situations, then switched to a less toxic maintenance agent
Upadacitinib	JAK1 inhibitor	Blocks Janus kinase 1 → inhibits downstream signalling of multiple cytokines (IL-6, IFN-γ, IL-12, IL-23)	Phase III trial (SELECT-GCA, 2024) showed efficacy in GCA; emerging data in TA; represents a future oral option
Abatacept	CTLA4-Ig fusion protein	Blocks T-cell co-stimulation (CD80/86–CD28 interaction)	Phase II trial (ABROGATE) showed some benefit in preventing relapse in TA; not yet standard of care

2. Vascular / Surgical Intervention

Surgery is not the first-line treatment. It is reserved for patients with structural complications that cause significant ischaemia or are life-threatening, despite optimal medical therapy:

Indication	Examples
Critical limb ischaemia	Severe claudication limiting daily activities; rest pain; tissue loss
Cerebrovascular insufficiency	Recurrent TIA/stroke despite medical therapy; critical carotid/vertebral stenosis
Renovascular hypertension	Refractory hypertension despite maximal medical therapy; progressive renal impairment from bilateral renal artery stenosis
Coronary ischaemia	Angina from coronary ostial stenosis unresponsive to medical therapy
Aortic regurgitation	Symptomatic severe AR requiring valve repair/replacement
Aortic aneurysm	Rapidly expanding or large aneurysm at risk of rupture/dissection
Coarctation-like lesion	Severe mid-aortic stenosis causing refractory hypertension and end-organ damage

Golden Rule: Quiescent Disease Before Surgery

Never operate on actively inflamed vessels. Active granulomatous inflammation weakens the vessel wall and impairs healing → surgical anastomoses are more likely to develop stenosis, pseudoaneurysm, or dehiscence. Disease should be in remission (clinical + imaging + laboratory) for at least 3 months before elective vascular surgery. If emergency surgery is unavoidable (e.g., rupturing aneurysm), concurrent high-dose steroids should be given perioperatively.

Procedure	Description	When to Consider
Bypass grafting	Using autologous vein (saphenous vein) or synthetic graft (PTFE/Dacron) to bypass stenosed/occluded segment	Preferred for long-segment stenosis/occlusion of aortic branches (subclavian, carotid, renal, iliac). Better long-term patency than endovascular procedures in TA
Endarterectomy	Surgical removal of intimal plaque/thickening	Rarely used in TA (unlike atherosclerotic carotid endarterectomy) because the disease involves the entire wall, not just the intima
Aortic reconstruction	Patch aortoplasty, interposition graft, or ascending-to-descending aortic bypass	For coarctation-like mid-aortic stenosis or extensive aortic disease
Aortic valve replacement (AVR)	Mechanical or bioprosthetic valve	For symptomatic severe aortic regurgitation from aortic root dilatation
Renal artery reconstruction	Bypass or reimplantation of renal artery	For refractory renovascular hypertension from renal artery stenosis

Procedure	Description	When to Consider
Percutaneous transluminal angioplasty (PTA) ± stenting	Balloon dilatation of stenosed segment ± metallic stent placement	For focal, short-segment stenosis (e.g., renal artery, subclavian artery). Less invasive than open surgery. However, restenosis rates are high in TA (30–50%) because the ongoing inflammatory process drives intimal hyperplasia in and around the stented segment
Aortic stent graft (TEVAR/EVAR)	Endovascular repair of aortic aneurysm	Selected cases of descending thoracic or abdominal aortic aneurysm; less data in TA than in atherosclerotic aneurysm

Key point for exams: Restenosis rates after endovascular procedures in TA are significantly higher than in atherosclerotic disease. This is because the underlying inflammatory process is not addressed by the stent. Open surgical bypass has better long-term patency but is more invasive. The decision is individualised.

3. Adjunctive / Supportive Measures

Hypertension is the most common complication and a major driver of cardiovascular morbidity
Most commonly due to renal artery stenosis → renovascular hypertension
Drug of choice: ACEI or ARB — because they directly counteract the RAAS activation driving the hypertension
- Caveat: If bilateral renal artery stenosis, ACEI/ARB can precipitate AKI (because GFR in the underperfused kidney becomes critically dependent on efferent arteriolar constriction by angiotensin II). Monitor creatinine closely after starting; may need calcium channel blockers (CCB) instead
Additional agents: Amlodipine (CCB), beta-blockers if needed
Target: BP < 130/80 mmHg (standard for patients with renal disease/vascular disease)
Important: Measure BP in the least affected limb (or legs if both arms are affected) to guide treatment — using a stenosed arm will give a falsely low reading

Low-dose aspirin (75–100 mg daily) is generally recommended for patients with arterial stenosis
Rationale: TA-damaged endothelium is prothrombotic; platelets aggregate at sites of stenosis → thrombotic occlusion is a major mechanism of acute ischaemic events (stroke, MI, acute limb ischaemia)
Aspirin inhibits cyclooxygenase-1 (COX-1) → reduces thromboxane A2 → decreases platelet aggregation
Gastroprotection: PPI (e.g., omeprazole) co-prescribed when aspirin is used with corticosteroids (dual GI ulcer risk)

Given that patients are on high-dose corticosteroids for prolonged periods, prophylaxis against steroid complications is essential:

Side Effect	Prophylactic Measure
Osteoporosis	Calcium 1000–1200 mg/day + Vitamin D 800–1000 IU/day from initiation; consider bisphosphonate (alendronate) if on steroids ≥ 3 months at ≥ 7.5 mg/day prednisolone equivalent; baseline DEXA scan
Steroid-induced diabetes	Monitor fasting glucose/HbA1c regularly; adjust DM medications if needed; be aware that steroid-induced hyperglycaemia typically affects postprandial glucose more than fasting
GI ulceration	PPI if concurrent aspirin/NSAID use
Adrenal suppression	Never stop steroids abruptly after prolonged use (≥ 3 weeks) → taper gradually. Educate patient about "sick day rules" (double dose during intercurrent illness) and to carry a steroid card/MedicAlert bracelet
Infections	Screen for latent TB (IGRA), HBV before immunosuppression; Pneumocystis jirovecii pneumonia (PJP) prophylaxis with co-trimoxazole if on prolonged high-dose steroids + another immunosuppressant
Cataracts / Glaucoma	Annual ophthalmology review
Avascular necrosis (AVN)	Counsel patients to report hip/knee pain; MRI if suspected

Screening	Rationale
IGRA + CXR	Latent TB — HK has higher TB incidence than most developed cities. If IGRA positive, treat LTBI with 9 months isoniazid (or 3 months isoniazid + rifampicin) before or concurrently with immunosuppression
HBsAg, anti-HBs, anti-HBc, HBV DNA	HBV reactivation risk under immunosuppression. If HBsAg+, start antiviral prophylaxis (entecavir or tenofovir)
Varicella IgG	If non-immune, consider vaccination before immunosuppression (live vaccine — cannot give once immunosuppressed)
Baseline FBC, LFT, RFT, urinalysis	Establish baseline for monitoring drug toxicity

Chronic inflammation in TA is itself a cardiovascular risk factor (accelerated atherosclerosis)
Additionally, long-term corticosteroids worsen metabolic syndrome (DM, dyslipidaemia, obesity, HTN)
Lipid management: Statin therapy if dyslipidaemic or high cardiovascular risk
Smoking cessation: Smoking worsens vascular disease and counteracts treatment
Exercise: Supervised exercise programme for patients with claudication (to build collateral circulation and improve functional capacity)

Given that TA predominantly affects women of reproductive age, pregnancy planning is a critical consideration:

Aspect	Management
Pre-conception	Ensure disease is quiescent for ≥ 6 months before conception; switch to pregnancy-safe medications
Medications in pregnancy	Safe: low-dose prednisolone ( < 20 mg/day), azathioprine. Contraindicated: methotrexate (teratogenic — stop 3 months prior), mycophenolate (teratogenic — stop 6 weeks prior), cyclophosphamide, tocilizumab (insufficient data)
Monitoring	Close BP monitoring (4-limb BP); serial echocardiography; fetal growth monitoring; multidisciplinary team (rheumatologist + obstetrician + cardiologist)
Risks	Pre-eclampsia (difficult to diagnose if baseline BP is abnormal from TA), IUGR, preterm birth, aortic dissection (rare but catastrophic in patients with aortic dilatation)
Delivery	Often elective Caesarean section if significant aortic root dilatation (to avoid Valsalva haemodynamic stress); epidural anaesthesia may be preferred over general anaesthesia

Domain	Method	Frequency
Clinical assessment	4-limb BP, pulse examination, symptom review (claudication, constitutional symptoms, new neurological symptoms)	Every visit (initially monthly, then 3–6 monthly)
Laboratory	ESR, CRP, FBC, LFT, RFT, glucose	Every 4–8 weeks during active treatment; 3–6 monthly in stable disease
Vascular imaging	MRA (preferred) or CTA	Every 6–12 months during first 2 years, then annually or with suspected flare
Echocardiography	AR, LV function, aortic root dimensions	Annually or with clinical change
Drug monitoring	FBC + LFT for MTX/AZA; lipids + neutrophil count for tocilizumab	Per drug protocol

Prognosis: chronic, relapsing/remitting course in majority, 80–90% 5-year survival ^[2]

Aspect	Detail
Natural history	Chronic, relapsing-remitting in most patients
Survival	5-year survival: 80–90%; 10-year survival: ~70–80%; major causes of death are heart failure, stroke, renal failure, and aortic rupture/dissection
Relapse	Very common (50–70%) during steroid taper; tocilizumab and steroid-sparing agents reduce relapse rates
Functional outcome	Many patients have significant disability from vascular complications (claudication, stroke sequelae, visual impairment, heart failure) even with treatment
Poor prognostic factors	Extensive disease (Type V), aortic regurgitation, aneurysm, retinopathy, progressive course despite treatment, complications at diagnosis

High Yield Summary — Management of Takayasu Arteritis

From GC Lecture Slides ^[1]:

High dose corticosteroids
Immunosuppressive drugs
Anti-IL6

Induction: Prednisolone 1 mg/kg/day for 2–4 weeks, then slow taper over 12–24 months

Steroid-sparing agents (start early): First-line = Methotrexate or Azathioprine. Second-line = Tocilizumab (anti-IL6)

Why steroid-sparing? Because 50–70% relapse on steroid taper alone; long-term steroids cause devastating side effects in young women

Tocilizumab caveat: Suppresses CRP production → CRP becomes unreliable for monitoring → must use imaging

Vascular surgery: Only when disease is quiescent; for critical ischaemia, refractory HTN, severe AR, or aneurysm at risk of rupture. Open bypass has better long-term patency than endovascular procedures in TA

Adjunctive: Antihypertensives (ACEI/ARB, beware bilateral RAS), low-dose aspirin, osteoporosis prophylaxis, TB/HBV screening before immunosuppression

Prognosis: Chronic relapsing-remitting, 80–90% 5-year survival

Active Recall - Management of Takayasu Arteritis

References

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (p89–90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (p96 — Section 3.6.2 Takayasu Arteritis) ^[3] Senior notes: Maksim Medicine Notes.pdf (p332 — Section 13.9 Vasculitis, Takayasu arteritis) ^[16] Senior notes: Ryan Ho Rheumatology.pdf (p95 — Section 3.6.1 GCA, treatment with tocilizumab)

Complications of Takayasu Arteritis

The complications of Takayasu arteritis arise from two fundamentally different sources:

Disease-related complications — direct consequences of the granulomatous inflammatory process causing stenosis, occlusion, or aneurysm of the aorta and its branches → end-organ ischaemia or structural failure
Treatment-related complications — side effects of the long-term immunosuppression required to control the disease (corticosteroids, MTX, AZA, tocilizumab)

These complications are the major determinants of morbidity and mortality in TA. The major causes of death are heart failure, stroke, renal failure, and aortic rupture/dissection.

The clinical features discussed in Part 1 (bruits, absent pulses, claudication, hypertension) are essentially the early manifestations of what, if untreated or inadequately treated, progress into the full-blown complications listed below. The progression from "symptom" to "complication" is a continuum.

1. Cardiovascular Complications

Aortic disease: aneurysm / AR ^[3]

Aspect	Detail
Frequency	20–25% of TA patients; the most common valvular complication
Mechanism	Granulomatous inflammation of the ascending aorta and aortic root → destruction of elastic lamina in the media → aortic root dilatation → annular dilatation → the aortic valve leaflets can no longer coapt → regurgitation. In some cases, direct inflammation of the valve leaflets contributes. TA is specifically listed as a cause of chronic AR due to root disease ^[17]
Pathophysiological consequences	Volume overload of the LV → LV dilatation → initially compensated (eccentric hypertrophy, increased SV) → eventually decompensated → LV systolic dysfunction → congestive heart failure
Clinical features	Early diastolic murmur (decrescendo, blowing, best heard at left sternal edge sitting forward in expiration); wide pulse pressure and collapsing pulse in chronic AR; signs of heart failure when decompensated
Management	Medical: vasodilators (ACEI/ARB, nifedipine) to reduce afterload; Surgical: aortic valve repair or replacement ± aortic root replacement (Bentall procedure) when symptomatic or severe LV dilatation/dysfunction. Must ensure disease is quiescent before surgery

Aspect	Detail
Frequency	One of the leading causes of mortality in TA
Mechanisms	Multiple converging pathways: (1) Aortic regurgitation → chronic volume overload → LV dilatation → systolic dysfunction. (2) Hypertension → chronic pressure overload → LVH → diastolic then systolic dysfunction. (3) Coronary ostial stenosis → myocardial ischaemia → ischaemic cardiomyopathy. (4) Myocarditis — TA can directly cause autoimmune myocarditis (TA is listed as a cause of autoimmune myocarditis ^[18]). (5) Pulmonary hypertension → RV failure
Clinical features	Dyspnoea, orthopnoea, PND, peripheral oedema, elevated JVP, bibasal crackles, displaced apex, S3 gallop

Ischaemia: angina ^[3]

Aspect	Detail
Mechanism	Granulomatous inflammation extends to the coronary ostia or proximal coronary arteries → stenosis → reduced coronary blood flow → angina and potentially MI. This is a non-atherosclerotic cause of CAD ^[5]
Why ostial?	The coronary arteries arise from the aortic sinuses (of Valsalva), which are directly adjacent to the ascending aorta. When the ascending aorta is inflamed, the process extends to the coronary ostia by contiguity — not the mid-vessel atherosclerotic pattern
Clinical implication	Young woman presenting with angina or acute MI without traditional cardiovascular risk factors → consider TA as the cause. Standard angiography may show ostial stenosis only
Management	CABG (preferred over PCI due to ostial location and inflammation); medical: anti-anginals + immunosuppression for underlying TA

Aspect	Detail
Mechanism	Destruction of the elastic media and smooth muscle by granulomatous inflammation → weakening of the vessel wall → dilatation → true aneurysm formation. Can affect thoracic aorta, abdominal aorta, or both
Risk	Rupture (catastrophic haemorrhage), aortic dissection, compression of adjacent structures (recurrent laryngeal nerve → hoarseness; oesophagus → dysphagia; bronchus → stridor)
Monitoring	Serial CTA or MRA to track aneurysm dimensions; surgical repair if rapidly expanding or exceeding size thresholds

Risk factors for aortic dissection: Vasculitis, e.g. Takayasu arteritis ^[19]

Aspect	Detail
Mechanism	The weakened, inflamed aortic wall is vulnerable to intimal tears. Contributing factors: (1) Inflammatory destruction of elastic fibres in the media → structural weakness. (2) Concomitant hypertension → increased wall stress (Laplace's law: wall tension = pressure × radius / wall thickness; as the wall thins and pressure rises, tension escalates). (3) Aneurysmal dilatation increases radius → further increases wall tension
Clinical features	Sudden onset tearing chest/back pain, asymmetric BP/pulses (may already exist from TA), signs of organ ischaemia (MI, stroke, limb ischaemia, AKI, mesenteric ischaemia) ^[19]
Complications of dissection	Type A: AR, cardiac tamponade, MI, stroke. Type B: coeliac/renal/LL ischaemia, spinal ischaemia ^[19]^[20]
Management	Type A: emergency surgical repair. Type B: medical management (BP control with IV labetalol/esmolol) unless complicated (end-organ ischaemia, expanding, rupture) → then TEVAR or open repair

Aortic Dissection in TA — High Yield

TA is explicitly listed as a risk factor for aortic dissection ^[19]. In any young patient presenting with acute aortic syndrome without the usual risk factors (hypertension in an elderly patient, Marfan syndrome), consider underlying TA. The pre-existing aortic wall inflammation and structural damage predispose to both dissection and rupture.

2. Cerebrovascular Complications

Ischaemia: stroke/TIA ^[3]

Aspect	Detail
Mechanism	Stenosis or occlusion of the common carotid arteries and/or vertebral arteries → reduced cerebral perfusion → thrombotic or haemodynamic ischaemic stroke. TA is classified as a cause of large vessel extracranial ischaemic stroke ^[6]
Types	(1) Haemodynamic stroke — chronic hypoperfusion from bilateral carotid stenosis → watershed/boundary zone infarcts. (2) Thrombotic stroke — thrombus forming at the site of stenosis → occlusion. (3) Hypertensive stroke — if concomitant uncontrolled renovascular HTN → intracerebral haemorrhage
Clinical features	Depend on territory: anterior circulation (carotid) → contralateral hemiparesis/hemisensory loss, aphasia, amaurosis fugax; posterior circulation (vertebral/basilar) → vertigo, diplopia, ataxia, dysarthria, visual field defects
Significance	Stroke is one of the leading causes of morbidity in TA; young women with stroke should be evaluated for vasculitis including TA

Subclavian steal syndrome ^[3]

Aspect	Detail
Mechanism	Severe stenosis or occlusion of the subclavian artery proximal to the vertebral artery origin → during ipsilateral arm exercise → blood "steals" retrograde down the vertebral artery to supply the arm → vertebrobasilar territory ischaemia
Clinical features	Dizziness, vertigo, syncope, visual blurring — all provoked by ipsilateral arm exercise. BP difference > 20 mmHg between arms is suggestive
Diagnosis	Doppler USG shows reversed flow in the ipsilateral vertebral artery; CTA/MRA confirms subclavian stenosis

3. Renovascular Complications

↑BP: renal artery stenosis ^[3]

Aspect	Detail
Frequency	The most common complication of TA overall; HTN affects > 50% of patients ^[2]
Mechanism	Renal artery stenosis → ↓renal perfusion → juxtaglomerular cells sense ↓perfusion pressure → ↑renin secretion → renin cleaves angiotensinogen → angiotensin I → ACE converts to angiotensin II → (1) systemic vasoconstriction, (2) aldosterone secretion from adrenal cortex → Na⁺/H₂O retention → hypertension. Also: ↓aortic compliance from fibrosed, stiff aorta → systolic hypertension
Clinical significance	Hypertension is often severe and refractory to standard medical therapy; may present as malignant/accelerated hypertension with end-organ damage (hypertensive retinopathy, LVH, proteinuria, hypertensive encephalopathy)
Complications of hypertension	LVH → heart failure; hypertensive nephropathy → CKD; hypertensive retinopathy → visual impairment; stroke (both ischaemic and haemorrhagic)
Important trap	Arm BP may be falsely low due to subclavian stenosis → true hypertension is masked → end-organ damage develops silently

Aspect	Detail
Mechanism	(1) Chronic renal artery stenosis → ischaemic nephropathy → progressive renal atrophy and CKD. (2) Hypertensive nephrosclerosis. (3) ACEI/ARB-induced AKI if bilateral RAS (efferent arteriolar dilatation → ↓↓GFR)
Monitoring	Serial RFT, renal duplex USG for kidney size asymmetry and renal artery flow velocities

A. Critical Limb Ischaemia

Ischaemia: Limb claudication ^[3]

Aspect	Detail
Mechanism	Progressive stenosis/occlusion of subclavian, axillary, iliac, or femoral arteries → initially intermittent claudication (exertional ischaemia) → if disease progresses → rest pain, tissue loss, gangrene
Upper vs lower limb	Upper limb ischaemia is more characteristic of TA (subclavian/axillary involvement) than of atherosclerotic PAD (which predominantly affects lower limbs)
Progression	Non-critical claudication → critical limb ischaemia (rest pain, ulcers, gangrene, ankle SBP < 50 mmHg) ^[21]
Complications of critical ischaemia	After revascularisation: reperfusion injury → compartment syndrome (pain out of proportion, pain with passive stretch → emergent fasciotomy) and rhabdomyolysis (K⁺ release, myoglobin → AKI, arrhythmia) ^[21]

Ischaemia: mesenteric ischemia ^[3]

Aspect	Detail
Mechanism	Stenosis of the coeliac trunk, superior mesenteric artery (SMA), or inferior mesenteric artery (IMA) → chronic mesenteric ischaemia ("intestinal angina")
Clinical features	Postprandial abdominal pain (15–30 minutes after eating due to increased metabolic demand of the gut exceeding the stenosed blood supply), food avoidance ("sitophobia"), significant weight loss
Risk of acute mesenteric ischaemia	If thrombosis occurs at the site of a critical stenosis → acute bowel infarction → peritonitis → sepsis → a surgical emergency with high mortality

Complication	Mechanism
Takayasu retinopathy	Chronic retinal hypoperfusion from carotid stenosis → retinal ischaemia → microaneurysm formation, arteriovenous anastomoses (the original finding described by Takayasu in 1908), cotton-wool spots, retinal haemorrhages. Classified into 4 stages. Advanced stages can lead to neovascularisation (like diabetic retinopathy) → vitreous haemorrhage, tractional retinal detachment
Amaurosis fugax	Transient monocular visual loss from carotid or ophthalmic artery stenosis → brief retinal ischaemia → "curtain coming down" over vision lasting seconds to minutes, then recovering completely
Hypertensive retinopathy	From renovascular hypertension → arteriolar narrowing, AV nicking, flame haemorrhages, cotton-wool spots, papilloedema (Modified Scheie classification) ^[22]

Aspect	Detail
Pulmonary artery involvement	TA involves the pulmonary arteries in up to 50% of cases on imaging (often subclinical). Stenosis of pulmonary arteries → increased pulmonary vascular resistance → pulmonary hypertension → RV pressure overload → RV dilatation → right heart failure
Clinical features	Dyspnoea on exertion, syncope, chest pain, haemoptysis; on exam: loud P2, RV heave, elevated JVP, peripheral oedema, hepatomegaly
Significance	Pulmonary artery involvement is unique to TA among the large vessel vasculitides (GCA essentially never involves pulmonary arteries) — this is a distinguishing feature ^[4]

These are not complications of TA itself, but of the prolonged immunosuppression required to manage it. In young women who may be on treatment for decades, these are major contributors to morbidity.

Long-term high-dose corticosteroids cause a predictable constellation of adverse effects:

Side Effect	Mechanism	Prevention/Management
Osteoporosis	Steroids inhibit osteoblast activity, enhance osteoclast activity, reduce Ca²⁺ absorption, increase renal Ca²⁺ excretion → net bone loss	Calcium + Vitamin D supplementation; bisphosphonate if ≥ 7.5 mg prednisolone for ≥ 3 months; baseline DEXA
Steroid-induced diabetes	Steroids increase hepatic gluconeogenesis, reduce peripheral glucose uptake (insulin resistance), impair β-cell function	Monitor fasting glucose/HbA1c; metformin or insulin as needed
Cushing syndrome	Exogenous hypercortisolism → central obesity, moon facies, buffalo hump, striae, thin skin, proximal myopathy	Minimise steroid dose using steroid-sparing agents
Avascular necrosis (AVN)	Steroids cause fat embolism and endothelial dysfunction in end-arteries supplying bone → ischaemic necrosis, typically femoral head	Counsel patients to report hip/knee pain; MRI for early detection
Infections	Immunosuppression → susceptibility to opportunistic infections (TB reactivation, PJP, fungal, viral)	IGRA + CXR before starting; PJP prophylaxis (co-trimoxazole) if prolonged high-dose steroids; annual influenza/COVID vaccination
Adrenal suppression	Chronic exogenous steroids suppress the HPA axis → adrenal atrophy → unable to mount cortisol response to stress	Never stop abruptly; taper slowly; steroid card; sick-day rules (double dose during illness)
Cataracts and glaucoma	Posterior subcapsular cataracts from altered lens protein metabolism; glaucoma from decreased aqueous outflow	Annual ophthalmology review
Peptic ulcer disease	Steroids impair gastric mucosal defence (reduce prostaglandin synthesis); risk compounded by concurrent aspirin	PPI co-prescription if on aspirin
Psychiatric effects	Insomnia, mood disturbance, psychosis (rare at high doses)	Counsel patients; consider dose adjustment

Side Effect	Mechanism
Hepatotoxicity	Direct hepatocyte toxicity; risk of fibrosis/cirrhosis with cumulative dose
Myelosuppression	Folate antagonism → impaired haematopoiesis → pancytopenia
Pneumonitis	Hypersensitivity reaction → acute interstitial pneumonitis (cough, dyspnoea, fever) — must distinguish from infection
Teratogenicity	Folate antagonism disrupts embryogenesis → absolutely contraindicated in pregnancy
Mucositis	Folate deficiency → impaired mucosal cell turnover → oral ulcers, GI upset

Side Effect	Mechanism
Myelosuppression	Purine synthesis inhibition → especially severe if TPMT-deficient
Hepatotoxicity	Direct hepatocyte injury
GI upset	Nausea, vomiting, diarrhoea
Increased infection risk	Lymphocyte suppression
Lymphoma risk	Small increased risk with long-term use (EBV-driven in some cases)

Side Effect	Mechanism
Infections	IL-6 blockade impairs acute-phase response and neutrophil recruitment → ↑susceptibility especially to lower respiratory tract infections
GI perforation	IL-6 involved in gut mucosal repair; blockade may ↑risk especially with concurrent steroids and diverticular disease
Hyperlipidaemia	IL-6 normally suppresses lipoprotein lipase; blocking IL-6 → ↑LDL, ↑total cholesterol
Neutropenia	IL-6 promotes neutrophil production; blocking it can cause dose-dependent neutropenia
Masked infection	CRP suppressed by the drug → fever and CRP no longer rise normally in response to infection → infections may be diagnosed late

Treatment Complication Awareness

In any TA patient on long-term immunosuppression who develops new symptoms, always consider treatment complications alongside disease flare:

New dyspnoea → drug-induced pneumonitis (MTX)? Opportunistic infection (PJP, TB reactivation)? Or disease flare (pulmonary artery involvement)?
New hip pain → AVN from steroids? Or musculoskeletal complaint from disease?
Abnormal FBC → drug-induced myelosuppression (MTX, AZA)? Or anaemia of chronic disease from TA?
Rising glucose → steroid-induced diabetes? Or pre-existing DM worsened by steroids?

Given that TA predominantly affects women of reproductive age, pregnancy carries specific risks:

Complication	Mechanism
Pre-eclampsia	Difficult to diagnose because baseline BP is already abnormal and may be unmeasurable in affected arms; underlying renovascular HTN predisposes
Intrauterine growth restriction (IUGR)	Aortic/iliac stenosis → reduced uteroplacental blood flow → fetal growth restriction
Preterm birth	Related to disease activity, hypertension, and medications
Aortic dissection	Pregnancy is itself a risk factor for dissection (hormonal changes, haemodynamic stress); TA provides the structural vulnerability. Highest risk in third trimester and peripartum
Flare during pregnancy	Disease may flare, especially if immunosuppression is reduced; corticosteroids are safe in pregnancy, but MTX and MMF must be stopped

Organ System	Complication	Mechanism
Cardiovascular	AR, heart failure, MI, aortic aneurysm, aortic dissection	Root dilatation → AR → volume overload; coronary ostial stenosis → MI; media destruction → aneurysm/dissection
Cerebrovascular	Stroke, TIA, subclavian steal	Carotid/vertebral stenosis → cerebral hypoperfusion/thrombosis
Renal	Renovascular HTN, CKD	Renal artery stenosis → RAAS activation → HTN; ischaemic nephropathy
Limb	Claudication, critical limb ischaemia	Subclavian/iliac stenosis → exertional then rest ischaemia
Mesenteric	Chronic/acute mesenteric ischaemia	Coeliac/SMA stenosis → intestinal angina; thrombosis → bowel infarction
Ophthalmological	Takayasu retinopathy, amaurosis fugax, hypertensive retinopathy	Carotid stenosis → retinal hypoperfusion; renovascular HTN
Pulmonary	Pulmonary hypertension, RV failure	Pulmonary artery stenosis → ↑PVR
Treatment-related	Osteoporosis, DM, infections, AVN, myelosuppression, teratogenicity	Corticosteroid and immunosuppressant toxicity
Pregnancy	Pre-eclampsia, IUGR, dissection, flare	Altered haemodynamics + structural vulnerability + medication constraints

High Yield Summary — Complications of Takayasu Arteritis

Leading causes of death: Heart failure, stroke, renal failure, aortic rupture/dissection

Most common complication: Renovascular hypertension ( > 50%) — from renal artery stenosis → RAAS activation

Most common valvular complication: Aortic regurgitation (20-25%) — from aortic root dilatation

Aortic dissection: TA is a recognised risk factor ^[19] — weakened media + hypertension + aneurysmal dilatation → intimal tear

Coronary involvement: Ostial stenosis (non-atherosclerotic CAD) → angina/MI in a young woman

Cerebrovascular: Carotid/vertebral stenosis → stroke/TIA; subclavian steal syndrome

Pulmonary: Pulmonary artery involvement (unique to TA among LVV) → pulmonary HTN

Don't forget treatment complications: Steroids (osteoporosis, DM, AVN, infections, adrenal suppression); MTX (hepatotoxicity, teratogenicity, pneumonitis); Tocilizumab (masked infections — CRP unreliable)

Pregnancy: High-risk — pre-eclampsia, IUGR, risk of aortic dissection; MTX/MMF absolutely contraindicated

Active Recall - Complications of Takayasu Arteritis

References

^[1] Lecture slides: GC 053. Fingers turn white and blue.pdf (p89–90) ^[2] Senior notes: Ryan Ho Rheumatology.pdf (p96 — Section 3.6.2 Takayasu Arteritis) ^[3] Senior notes: Maksim Medicine Notes.pdf (p332 — Section 13.9 Vasculitis, Takayasu arteritis) ^[4] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1766 — Vasculitis subtypes comparison table) ^[5] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p384–395 — Non-atherosclerotic CAD causes) ^[6] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1213 — Causes of ischaemic stroke) ^[17] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p472 — Causes of aortic regurgitation) ^[18] Senior notes: Ryan Ho Cardiology.pdf (p165 — Myocarditis, autoimmune causes including Takayasu arteritis) ^[19] Senior notes: Maksim Medicine Notes.pdf (p15 — Aortic dissection, risk factors including Takayasu arteritis) ^[20] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p610 — Complications of aortic dissection) ^[21] Senior notes: Ryan Ho Cardiology.pdf (p212 — Chronic limb ischaemia, complications) ^[22] Senior notes: Ryan Ho Ophthalmology.pdf (p73 — Hypertensive retinopathy)

High Yield Summary

Definition: Granulomatous large vessel vasculitis of the aorta and its major branches, a.k.a. "pulseless disease" / "aortic arch syndrome" / "occlusive thromboaortopathy"

Epidemiology: Young women (10–40 years), F:M ~8–9:1 in Asians, more common in Asians

Key Clinical Features (exam favourites, from GC lecture slides):

Bruits (80%), Claudication (70%), Decreased pulses (60%), Arthralgias (50%), Asymmetric BP (50%), Constitutional symptoms (40%), Hypertension (30%)