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Vasculitis for the American Board of Internal Medicine (ABIM) Exam

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Overview of Vasculitis
    • Definition: Vasculitis refers to inflammation of blood vessels, leading to changes such as thickening, weakening, narrowing, or scarring of the vessel walls.
    • Classification:
  • Large vessel vasculitis: Affects large arteries (e.g., giant cell arteritis, Takayasu arteritis).
  • Medium vessel vasculitis: Affects medium-sized arteries (e.g., polyarteritis nodosa, Kawasaki disease).
  • Small vessel vasculitis: Affects small arteries, arterioles, capillaries, and venules (e.g., granulomatosis with polyangiitis, microscopic polyangiitis, Henoch-Schönlein purpura).
    • Etiology:
    • Idiopathic (most common).
    • Secondary causes: Infections, drugs, malignancies, autoimmune disorders.
Clinical Features
    • General Symptoms:
  • Fever, fatigue, weight loss, and myalgia are common systemic symptoms.
  • Localized symptoms depend on the organs involved.
    • Large Vessel Vasculitis:
    • Giant cell arteritis: Headache, scalp tenderness, jaw claudication, visual disturbances.
    • Takayasu arteritis: Limb claudication, absent pulses, differences in blood pressure between arms.
    • Medium Vessel Vasculitis:
    • Polyarteritis nodosa (PAN): Abdominal pain, hypertension, renal involvement, mononeuritis multiplex.
    • Kawasaki disease: Fever, conjunctivitis, mucocutaneous changes, coronary artery aneurysms.
    • Small Vessel Vasculitis:
    • Granulomatosis with polyangiitis (GPA): Upper and lower respiratory tract involvement, glomerulonephritis.
    • Microscopic polyangiitis (MPA): Pulmonary hemorrhage, glomerulonephritis.
    • Henoch-Schönlein purpura (HSP): Palpable purpura, abdominal pain, arthralgia, renal involvement.
Diagnosis
    • Laboratory Tests:
  • Increased ESR and CRP, indicating inflammation.
  • Autoantibodies:
    • ANCA (for GPA and MPA).
    • Anti-GBM (Goodpasture syndrome with RPGN).
    • Elevated IgA (for HSP).
    • ANA and rheumatoid factor (in some types of secondary vasculitis).
  • Anemia of chronic disease, leukocytosis, and elevated creatinine in cases with renal involvement.
    • Imaging:
  • Angiography (CT or MRI): Useful for large and medium vessel vasculitis to detect vessel stenosis or aneurysms.
  • PET scan: May help in detecting active inflammation in large vessel vasculitis.
    • Biopsy:
  • Gold standard for definitive diagnosis, particularly in suspected cases of small vessel vasculitis.
Treatment
    • Corticosteroids:
  • First-line treatment for most forms of vasculitis.
  • High-dose steroids are used initially, followed by a tapering regimen.
    • Immunosuppressive Agents:
  • Cyclophosphamide, methotrexate, azathioprine: Often used in conjunction with corticosteroids for more severe or refractory cases.
  • Rituximab: Commonly used in ANCA-associated vasculitis (GPA, MPA).
    • Biologics:
    • Tocilizumab: Approved for giant cell arteritis.
    • IVIG: Used for Kawasaki disease.
Essential Points
    • Vasculitis is classified by the size of the affected vessels: large, medium, or small.
    • Diagnosis requires a combination of clinical suspicion, laboratory testing (e.g., ANCA), imaging, and often biopsy.
    • Prompt treatment with corticosteroids and immunosuppressants can prevent serious complications.
    • Some forms, such as giant cell arteritis and ANCA-associated vasculitis, are medical emergencies due to the risk of vision loss or organ damage.
    • Drug toxicity monitoring and prevention are critical to limit long-term damage from therapies, especially glucocorticoids and immunosuppressive agents.