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Large Vessel Vasculitis for USMLE Step 2

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Large Vessel Vasculitis for the USMLE Step 2 Exam
Large Vessel Vasculitis
Large vessel vasculitis includes two primary types: Giant Cell Arteritis (GCA) and Takayasu Arteritis (TA), both of which affect the aorta and its major branches. GCA primarily affects older adults, while TA is more common in younger individuals.
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Giant Cell Arteritis (GCA)
  • Definition:
    • Also called temporal arteritis, GCA is an inflammatory vasculitis that affects the aorta and its cranial branches, especially the temporal arteries.
    • Frequently associated with polymyalgia rheumatica (PMR).
Large vessel vasculitis vessels
  • Epidemiology:
    • Primarily affects adults over 50 years, with higher incidence in women and those of Northern European ancestry.
  • Pathophysiology:
    • Characterized by granulomatous inflammation with giant cells, leading to thickening of the arterial wall and luminal narrowing.
    • Chronic inflammation can cause ischemia, particularly in cranial arteries, resulting in potential vision loss.
  • Clinical Presentation:
    • Systemic Symptoms: Fever, fatigue, weight loss, and malaise.
    • Headache: Severe, often located in the temporal area with associated scalp tenderness.
    • Jaw Claudication: Pain in the jaw when chewing due to masseter ischemia.
    • Visual Disturbances: Amaurosis fugax (transient vision loss), which can progress to blindness if untreated.
    • Polymyalgia Rheumatica (PMR): Commonly coexists, with symptoms of proximal muscle pain and stiffness in shoulders and hips.
  • Diagnosis:
    • Elevated ESR and CRP: High ESR and CRP are sensitive markers for GCA.
    • Temporal Artery Biopsy: Gold standard for diagnosis, showing mononuclear cell infiltration, giant cells, and fragmentation of the internal elastic lamina.
    • Imaging: Doppler ultrasound may reveal a “halo sign” around inflamed arteries; MRI/CT angiography is useful to assess aortic involvement.
  • Management:
    • Corticosteroids: High-dose prednisone (40-60 mg/day) is the mainstay to reduce inflammation and prevent vision loss.
    • Tocilizumab: IL-6 receptor antagonist used as adjunctive therapy for relapsing GCA cases.
    • Aspirin: Low-dose aspirin is sometimes added to reduce the risk of ischemic complications.
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Takayasu Arteritis (TA)
  • Definition:
    • Takayasu arteritis is a granulomatous vasculitis affecting the aorta and its major branches, often resulting in stenosis, occlusion, or aneurysmal changes.
    • Sometimes referred to as “pulseless disease” due to diminished pulses in affected extremities.
  • Epidemiology:
    • Primarily affects young women under 40, especially of Asian or Latin American descent.
  • Pathophysiology:
    • Similar to GCA, TA involves granulomatous inflammation in the vessel wall, leading to fibrosis, stenosis, and vascular remodeling over time.
  • Clinical Presentation:
    • Systemic Symptoms: Fever, fatigue, weight loss.
    • Vascular Symptoms:
    • Upper Limb Claudication: Pain and fatigue in the arms due to reduced blood flow.
    • Diminished Pulses and Bruits: Reduced or absent pulses, often with bruits over affected arteries.
    • Blood Pressure Discrepancies: Significant differences in blood pressure between arms.
    • Hypertension: Due to renal artery stenosis, often resulting in renovascular hypertension.
  • Diagnosis:
    • Elevated ESR and CRP: Indicators of systemic inflammation but nonspecific.
    • Imaging:
    • MRI Angiography (MRA) and CT Angiography (CTA): Primary tools to visualize arterial stenosis, occlusions, or aneurysms.
    • Conventional Angiography: Provides detailed arterial mapping but is less commonly used today due to availability of non-invasive imaging.
  • Management:
    • Corticosteroids: First-line treatment, typically with prednisone (1 mg/kg/day), followed by a slow taper once symptoms improve.
    • Immunosuppressive Agents: Methotrexate, azathioprine, or mycophenolate mofetil may be added for steroid-sparing or refractory cases.
    • Biologics: IL-6 inhibitors (e.g., tocilizumab) and TNF-alpha inhibitors for refractory TA cases.
    • Revascularization: Angioplasty or surgical bypass for severe stenosis causing significant ischemia or organ dysfunction.
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Key Points
  • Giant Cell Arteritis (GCA):
    • Common in adults >50 years; symptoms include temporal headache, jaw claudication, visual disturbances, and association with polymyalgia rheumatica.
    • Diagnosed by elevated ESR/CRP and temporal artery biopsy.
    • Treated with high-dose corticosteroids to prevent vision loss; tocilizumab may be added in refractory cases.
  • Takayasu Arteritis (TA):
    • Affects young women, especially of Asian or Latin American descent; presents with limb claudication, diminished pulses, blood pressure discrepancies, and hypertension.
    • Diagnosed primarily with MRA or CTA imaging; treated with corticosteroids, with immunosuppressants or biologics for refractory cases.
  • Similarities and Differences:
    • Both GCA and TA involve granulomatous inflammation of large vessels but differ in age group and vessel location affected.
    • Corticosteroids are the primary treatment; tocilizumab may be used for steroid-sparing in cases resistant to initial therapy.
  • Complications:
    • GCA: Risk of vision loss, aortic aneurysm.
    • TA: Hypertension, limb ischemia, and aortic aneurysms or dissections requiring close monitoring and potential intervention.

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