Takayasu Arteritis

A large vessel granulomatous vasculitis predominantly affecting the aorta and its major branches, occurring characteristically in young women, typically under forty years of age, with a disproportionately high prevalence in populations of Asian descent, producing progressive arterial stenosis, occlusion and, less commonly, aneurysm formation.

Pathophysiology

Granulomatous inflammation of the vessel wall, beginning in the adventitia and media, produces progressive intimal thickening and fibrosis, leading to luminal narrowing and, in the chronic fibrotic phase, the characteristic stenotic and occlusive arterial lesions that define established disease. An earlier, often clinically silent, inflammatory phase precedes the development of these fixed structural changes, contributing to frequent delayed diagnosis.

An early inflammatory phase presents non specifically with constitutional symptoms (fever, malaise, weight loss, arthralgia) and is frequently missed given the absence of localising vascular symptoms at this stage.

A later occlusive phase presents with symptoms of vascular insufficiency corresponding to the affected territory, including limb claudication (particularly upper limb, given the predilection for subclavian involvement), asymmetrical or absent pulses, blood pressure discrepancy between limbs, and vascular bruits over affected vessels.

Hypertension, often severe and difficult to control, is common and frequently reflects renal artery involvement.

Neurological symptoms including dizziness, syncope and visual disturbance occur with significant carotid or vertebral artery involvement, and stroke is a recognised serious complication.

Cardiac involvement includes aortic regurgitation from aortic root dilation, coronary artery involvement causing angina or myocardial infarction, and heart failure.

The combination of a young woman with unexplained hypertension, asymmetrical pulses or blood pressures, and vascular bruits should prompt consideration of this diagnosis, which is frequently delayed given the non specific nature of the early symptoms.

Imaging is central to diagnosis, with magnetic resonance angiography or computed tomography angiography demonstrating characteristic vessel wall thickening, stenosis, occlusion or aneurysm formation of the aorta and its major branches, and magnetic resonance imaging offering the additional advantage of detecting active vessel wall inflammation (oedema, enhancement) even before fixed structural changes develop.

Positron emission tomography combined with computed tomography is useful for detecting active vascular inflammation, particularly in the early phase before structural changes are established, and for monitoring disease activity during treatment.

Conventional catheter angiography, historically the diagnostic standard, remains useful for detailed anatomical assessment, particularly when planning interventional or surgical treatment.

Inflammatory markers (erythrocyte sedimentation rate, C reactive protein) are frequently elevated during active disease but correlate imperfectly with disease activity as assessed by imaging, and normal markers do not reliably exclude ongoing vascular inflammation.

Blood pressure should be measured in all four limbs given the frequency of asymmetrical involvement, and careful pulse examination performed at every assessment.

High dose corticosteroids are first line for active disease, producing improvement in constitutional symptoms and inflammatory markers, though vascular structural changes, once established, do not reverse with medical treatment alone.

Steroid sparing immunosuppression (methotrexate, azathioprine, mycophenolate mofetil) is introduced for relapsing or corticosteroid dependent disease, with tocilizumab or tumour necrosis factor inhibitors used for refractory cases given increasing evidence supporting their efficacy in this condition.

Aggressive blood pressure control is essential given the frequency and severity of hypertension, often complicated by renal artery involvement affecting choice and efficacy of antihypertensive agents.

Antiplatelet therapy is commonly used given the elevated risk of ischaemic complications from the underlying arteriopathy, though evidence for this specific practice is limited.

Revascularisation, by endovascular angioplasty or surgical bypass, is considered for critical stenosis causing significant symptoms or end organ ischaemia, ideally performed during a period of quiescent disease activity given the higher risk of restenosis or graft failure if undertaken during active inflammation.

Long term surveillance with regular clinical assessment, inflammatory markers and periodic vascular imaging is essential given the typically relapsing remitting course and the risk of silent progression of vascular lesions even in the absence of overt symptoms, with lifelong follow up generally required.