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Medium & Variable-Sized Vasculitis for USMLE Step 2

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Medium & Variable-Sized Vasculitis for the USMLE Step 2 Exam
Medium and variable-sized vasculitis encompasses Polyarteritis Nodosa (PAN), Kawasaki Disease, Thromboangiitis Obliterans (Buerger’s Disease), and Behçet’s Disease. These vasculitides can affect medium-sized vessels, with Behçet’s Disease affecting vessels of various sizes.
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Polyarteritis Nodosa (PAN)
  • Definition:
    • PAN is a systemic necrotizing vasculitis affecting medium-sized arteries and sparing small vessels, commonly involving the renal, gastrointestinal, and peripheral nervous systems.
  • Epidemiology:
    • More common in adults, with a slight male predominance, and associated with hepatitis B virus (HBV) in a subset of cases.
  • Pathophysiology:
    • PAN involves immune-mediated inflammation leading to transmural necrosis and microaneurysms, particularly in organs like the kidneys and intestines.
  • Clinical Presentation:
    • Systemic: Fever, weight loss, and malaise.
    • Renal: Hypertension and renal ischemia, with a lack of glomerulonephritis.
    • Neurologic: Mononeuritis multiplex with asymmetric neuropathies.
    • Gastrointestinal: Postprandial abdominal pain and mesenteric ischemia.
    • Dermatologic: Livedo reticularis, nodules, and ulcers.
Polyarteritis Nodosa
  • Diagnosis:
    • Laboratory: Elevated ESR and CRP; may show hepatitis B markers.
    • Tissue Biopsy: Demonstrates transmural inflammation and fibrinoid necrosis.
    • Angiography: Reveals “beading” or aneurysms in renal or mesenteric arteries.
  • Management:
    • Corticosteroids: Main treatment.
    • Immunosuppressive Therapy: Cyclophosphamide in severe cases.
    • Antivirals: For HBV-associated PAN with corticosteroids.
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Kawasaki Disease
  • Definition:
    • A self-limited vasculitis of medium-sized vessels, primarily affecting children and often involving the coronary arteries.
  • Epidemiology:
    • Common in children under 5, especially in Asian populations.
  • Pathophysiology:
    • The exact cause is unknown, but an infectious trigger in genetically susceptible children is suspected, leading to coronary artery inflammation.
  • Clinical Presentation:
    • Fever: Lasts >5 days and is unresponsive to antipyretics.
    • Criteria (at least 4 of the following):
    • Bilateral non-exudative conjunctivitis.
    • Oral mucosal changes (strawberry tongue, cracked lips).
    • Polymorphous rash.
    • Extremity changes (erythema and edema).
    • Cervical lymphadenopathy >1.5 cm.
  • Complications:
    • Coronary artery aneurysms can develop, potentially leading to myocardial infarction in untreated cases.
  • Diagnosis:
    • Primarily clinical; laboratory findings include elevated ESR/CRP and thrombocytosis.
    • Echocardiography: To assess coronary aneurysms.
  • Management:
    • IVIG: Administered early to prevent coronary complications.
    • Aspirin: High-dose during the acute phase, followed by low-dose for thrombotic prevention.
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Thromboangiitis Obliterans (Buerger’s Disease)
  • Definition:
    • Non-atherosclerotic vasculitis affecting small- and medium-sized vessels, strongly associated with smoking.
  • Epidemiology:
    • Most common in young male smokers under 45.
  • Pathophysiology:
    • Thought to result from an immune response to tobacco, leading to vessel inflammation, thrombosis, and eventual vascular occlusion.
  • Clinical Presentation:
    • Ischemia: Claudication, rest pain, ulcers, and gangrene in the hands and feet.
    • Raynaud’s Phenomenon: Color changes in fingers/toes with cold.
    • Migratory Thrombophlebitis: Red, painful cords along veins.
  • Diagnosis:
    • Clinical diagnosis supported by history of heavy smoking.
    • Angiography: Shows corkscrew-shaped collaterals in affected vessels.
  • Management:
    • Smoking Cessation: Essential to halt progression.
    • Symptomatic Treatment: Pain management, wound care, and sometimes amputation in severe cases.
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Behçet’s Disease
  • Definition:
    • A variable vessel vasculitis affecting vessels of all sizes, characterized by recurrent oral and genital ulcers, uveitis, and systemic inflammation.
  • Epidemiology:
    • Most common in Middle Eastern and East Asian populations, affecting young adults.
  • Pathophysiology:
    • Likely an aberrant immune response to environmental triggers in genetically predisposed individuals.
  • Clinical Presentation:
    • Oral Ulcers: Painful, recurrent, and typically the first manifestation.
    • Genital Ulcers: Similar to oral ulcers but often deeper.
    • Ocular: Uveitis, which can lead to blindness.
    • Skin Lesions: Erythema nodosum and acne-like eruptions.
    • Vascular: Venous thrombosis, especially in large veins.
  • Diagnosis:
    • Based on clinical criteria: recurrent oral ulcers plus at least two of the following—genital ulcers, uveitis, skin lesions, or positive pathergy test.
  • Management:
    • Corticosteroids: For acute flares.
    • Immunosuppressive Therapy: Azathioprine or TNF inhibitors for more severe cases.
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Key Points
  • Polyarteritis Nodosa (PAN):
    • Affects medium-sized vessels; often presents with hypertension, neuropathy, and GI ischemia.
    • Diagnosed via biopsy or angiography; treated with corticosteroids and immunosuppressants.
  • Kawasaki Disease:
    • Affects children with prolonged fever and risk of coronary aneurysms.
    • Diagnosed clinically; treated with IVIG and aspirin.
  • Thromboangiitis Obliterans (Buerger’s Disease):
    • Affects young smokers, causing extremity ischemia and ulcers; smoking cessation is crucial.
  • Behçet’s Disease:
    • Variable vessel vasculitis with recurrent ulcers and uveitis.
    • Managed with corticosteroids for flares and immunosuppressants for severe cases.

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