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Large Vessel Vasculitis for USMLE Step 1

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Large Vessel Vasculitis for the USMLE Step 1 Exam
Large Vessel Vasculitis
Large vessel vasculitis includes two primary conditions: Giant Cell Arteritis (GCA) and Takayasu Arteritis (TA). These conditions are defined by inflammation in the aorta and major arteries, with distinct clinical presentations and demographic features.
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Giant Cell Arteritis (GCA)
  • Definition:
    • Also called temporal arteritis, GCA primarily affects the aorta and cranial branches, especially the temporal arteries.
    • Closely associated with polymyalgia rheumatica (PMR).
Large vessel vasculitis vessels
  • Epidemiology:
    • Occurs almost exclusively in adults >50 years old, with a higher incidence in women and those of Northern European descent.
  • Pathophysiology:
    • Characterized by granulomatous inflammation with giant cells within the arterial wall.
    • Leads to vessel wall thickening and lumen narrowing, which can cause ischemia, particularly in the head and neck.
  • Clinical Presentation:
    • Constitutional Symptoms: Fever, fatigue, weight loss.
    • Headache: Typically in the temporal region with scalp tenderness.
    • Jaw Claudication: Pain in the jaw muscles while chewing.
    • Visual Symptoms: Transient vision loss or “amaurosis fugax” that can lead to blindness if untreated.
    • Polymyalgia Rheumatica (PMR): Commonly co-occurs with GCA, causing pain and stiffness in the shoulders and hips.
  • Diagnosis:
    • Elevated ESR and CRP: Consistent markers of inflammation in GCA.
    • Temporal Artery Biopsy: Gold standard, showing mononuclear cell infiltration and giant cells.
    • Imaging: Doppler ultrasound may show a “halo sign” around inflamed temporal arteries.
  • Management:
    • Corticosteroids: High-dose prednisone to prevent ischemic complications, particularly vision loss.
    • Tocilizumab: An IL-6 receptor inhibitor, used as an adjunct to corticosteroids in cases of recurrent disease.
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Takayasu Arteritis (TA)
  • Definition:
    • Takayasu arteritis is a granulomatous vasculitis primarily affecting the aorta and its major branches, often called “pulseless disease” due to diminished pulses.
  • Epidemiology:
    • More common in young women, particularly of Asian or Latin American descent, usually presenting before age 40.
  • Pathophysiology:
    • Similar granulomatous inflammation as GCA but affects younger individuals.
    • Chronic inflammation can cause vessel stenosis, fibrosis, and occasionally aneurysms, often affecting the aorta and main branches.
  • Clinical Presentation:
    • Constitutional Symptoms: Fever, weight loss, fatigue.
    • Vascular Symptoms:
    • Upper Limb Claudication: Pain and fatigue in the arms with exertion.
    • Diminished Pulses: Weak or absent pulses in the arms and neck, often accompanied by bruits.
    • Blood Pressure Discrepancies: Notable differences in blood pressure between arms.
    • Hypertension: Due to renal artery stenosis, leading to renovascular hypertension.
  • Diagnosis:
    • Elevated ESR and CRP: Markers of inflammation but nonspecific.
    • Imaging:
    • MRI Angiography (MRA) or CT Angiography (CTA): Visualizes stenosis, occlusion, or aneurysms in large vessels.
    • Conventional Angiography: Used less frequently but provides detailed vessel mapping.
  • Management:
    • Corticosteroids: Prednisone to control inflammation, followed by a gradual taper.
    • Immunosuppressive Agents: Methotrexate or azathioprine may be added to corticosteroids for additional control.
    • Biologics: Agents like tocilizumab or TNF inhibitors in refractory cases.
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Key Points
  • Giant Cell Arteritis (GCA):
    • Affects adults >50, causing headaches, jaw claudication, and potential vision loss.
    • Diagnosed by elevated ESR/CRP and temporal artery biopsy.
    • Treated with high-dose corticosteroids to prevent vision loss; tocilizumab may be added for relapsing cases.
  • Takayasu Arteritis (TA):
    • Primarily affects young women, especially of Asian or Latin American descent.
    • Characterized by diminished pulses, arm claudication, blood pressure discrepancies, and renovascular hypertension.
    • Imaging with MRA or CTA is essential for diagnosis; treated with corticosteroids and immunosuppressive therapy if needed.
  • Similarities and Differences:
    • Both GCA and TA involve granulomatous inflammation of large vessels but affect different age groups and vessel locations.
    • Corticosteroids are the mainstay treatment, with immunosuppressive agents for refractory disease.
  • Complications:
    • GCA: Vision loss, stroke, aortic aneurysm.
    • TA: Severe hypertension, ischemia in affected limbs, aortic aneurysms or dissections.

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