Arteritis Takayasu

01Pathophysiology

Takayasu arteritis is a chronic granulomatous vasculitis that targets the aorta and its primary branches, making it a large vessel vasculitis. The disease begins in the adventitia and vasa vasorum (the tiny vessels that supply blood to the walls of large arteries), then progresses inward through the media to the intima.

The inflammatory process is driven predominantly by CD4+ T cells and macrophages, which infiltrate the vessel wall and form granulomas. These immune cells release pro-inflammatory cytokines, particularly IL-6, TNF-alpha, and interferon-gamma, which sustain the inflammatory cascade. The granulomatous inflammation destroys the elastic fibers and smooth muscle of the media, leading to two possible outcomes depending on the segment involved: fibrotic thickening with luminal narrowing (stenosis) or weakening of the wall with aneurysm formation.

This pathophysiology directly explains the biphasic clinical presentation. In the early (pre-pulseless) phase, systemic inflammation produces constitutional symptoms such as fever, fatigue, and weight loss. This phase is often misdiagnosed because the symptoms are nonspecific and vascular findings have not yet developed. In the late (occlusive) phase, progressive stenosis and occlusion of major arterial branches lead to end-organ ischemia. When the subclavian arteries are involved, patients lose their radial pulses and develop arm claudication. When the renal arteries are involved, the juxtaglomerular apparatus senses decreased perfusion and activates the renin-angiotensin-aldosterone system, producing secondary hypertension. When the carotid arteries are involved, cerebral hypoperfusion causes dizziness, syncope, and visual disturbances. Inflammation of the aortic root can cause aortic valve dilation and regurgitation.

The term "pulseless disease" derives from this late-stage loss of peripheral pulses, which is the hallmark physical finding that points toward the diagnosis.

02Classification and Clinical Manifestation

Angiographic Classification (Numano/Hata)

Type V is the most common pattern overall. Type I predominates in Japanese and Korean populations, while Types III, IV, and V are more common in Indian and Southeast Asian populations.

Clinical Manifestation by Phase

Vascular Complications

03Diagnostic Workup

When a young woman presents with constitutional symptoms and either absent pulses, blood pressure discrepancy between arms, or unexplained hypertension, the first step is to check inflammatory markers (ESR, CRP). These are almost always elevated in active disease and help support clinical suspicion, though normal values do not rule out chronic or "burned out" disease.

The best initial imaging test is CTA or MRA. CTA is widely available and provides excellent resolution for identifying wall thickening, stenosis, and aneurysms throughout the entire aorta and its branches. MRA is preferred for serial monitoring because it avoids radiation exposure, which is important in this young patient population. A hallmark finding on cross-sectional imaging is concentric wall thickening of the aorta, sometimes called the "macaroni sign" on CTA. Mural enhancement after contrast indicates active inflammation.

Conventional catheter-based angiography remains the most accurate test and has historically been the gold standard. It reveals the classic pattern of irregular narrowing with "skip lesions" (alternating segments of stenosis and normal or dilated vessel) and collateral formation. However, because it is invasive, it is now reserved for cases where noninvasive imaging is inconclusive or when vascular intervention is planned.

FDG-PET/CT is increasingly recognized as a valuable tool for detecting early, subclinical vascular inflammation before structural changes become apparent on CTA or MRA. It is particularly useful when the clinical suspicion is high but conventional imaging appears normal, and for assessing treatment response.

The 1990 ACR classification criteria (used for research classification, not strictly diagnosis) require at least 3 of the following 6: onset at age $\le \backslash leq$ 40, claudication of an extremity, decreased brachial artery pulse, blood pressure difference >10 mmHg between arms, bruit over the subclavian arteries or aorta, and arteriographic abnormality.

Biopsy is rarely performed because the involved vessels are not safely accessible for tissue sampling. When surgical specimens are obtained (e.g., during bypass), histology shows granulomatous inflammation with giant cells, destruction of the elastic lamina, and intimal fibrosis.

04Management and Treatment

Acute stabilization begins with high-dose glucocorticoids. Prednisone at 1 mg/kg/day (up to 60 mg) is the standard induction regimen. Most patients respond within weeks with improvement in symptoms and decline in ESR/CRP. Once remission is achieved, the dose is gradually tapered over many months. However, relapse rates during steroid tapering are high, occurring in roughly 50% of patients, which is why a steroid-sparing agent is typically introduced early.

Methotrexate (15 to 25 mg weekly, always given with folic acid 1 mg daily to reduce toxicity) is the preferred first-line steroid-sparing agent. Azathioprine and mycophenolate mofetil are reasonable alternatives. The goal is to maintain remission while minimizing cumulative steroid exposure.

For patients who relapse or are refractory to conventional immunosuppression, tocilizumab (an IL-6 receptor antagonist) has shown strong efficacy and is increasingly used. This is a high-yield point because the pathophysiology of Takayasu arteritis involves IL-6 as a central cytokine driving the granulomatous inflammation, making tocilizumab a biologically rational choice.

Low-dose aspirin is recommended in most patients to reduce the risk of arterial thrombosis in stenotic segments.

Blood pressure management is critical. Many patients develop renovascular hypertension that must be treated aggressively. ACE inhibitors or ARBs are preferred because they counteract the RAAS activation from renal artery stenosis. However, in patients with bilateral renal artery stenosis, these drugs can precipitate acute kidney injury by removing the angiotensin II-dependent efferent arteriolar tone that maintains GFR, so renal function must be monitored closely after initiation.

Vascular intervention (percutaneous transluminal angioplasty, stenting, or surgical bypass grafting) is considered for critical stenoses causing end-organ damage. A key principle is that interventions should be performed during periods of disease remission, because operating on actively inflamed vessels leads to higher rates of restenosis, anastomotic complications, and graft failure.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students get this diagnosis wrong is by failing to consider Takayasu arteritis in a young woman with unexplained hypertension or nonspecific constitutional symptoms. Because the early phase lacks vascular findings, these patients are frequently dismissed as having a viral illness or are misdiagnosed with other inflammatory conditions. The vignette writer's strategy is to present a young woman in her 20s with fatigue, weight loss, and a mildly elevated ESR, then bury the critical clue deep in the physical exam: an absent radial pulse on one side, a blood pressure difference between the arms, or a bruit heard over the neck or abdomen. If you do not actively look for these findings in the stem, you will miss the diagnosis.

A second common trap involves confusing Takayasu arteritis with Giant Cell Arteritis. Both are granulomatous large vessel vasculitides, and both can affect the aorta. The single most reliable discriminator is age: Takayasu is a disease of patients under 40, while GCA is a disease of patients over 50. If the vignette gives you a 25-year-old with aortitis, it is Takayasu. If it gives you a 68-year-old with aortitis, it is GCA. Do not overcomplicate this distinction.

A third trap is the timing of vascular intervention. Students often choose angioplasty or surgical bypass as the next best step in a patient with active inflammation and a stenotic artery. The correct answer is to achieve disease remission with immunosuppression first, then intervene surgically. Operating on inflamed vessels leads to complications and restenosis.

Finally, remember that ESR and CRP correlate with disease activity but are not perfectly reliable. Some patients with chronic, smoldering disease or "burned out" fibrotic lesions can have normal inflammatory markers despite ongoing vascular damage. Imaging (CTA, MRA, or PET-CT) is essential for assessing the true extent and activity of disease, and you should not rely on a normal ESR to exclude active vasculitis when the clinical picture is suggestive.

The core competency being tested is the ability to recognize a pattern of large vessel ischemia in a young patient, connect the physical exam findings (pulse deficits, pressure discrepancies, bruits) to underlying aortic branch disease, sequence the workup from inflammatory markers through noninvasive imaging to angiography, and understand that immunosuppression must precede revascularization.