Necrotizing vasculitis affecting capillaries, arterioles and small venules is characteristic of which disease?

• A. Wegener granulomatosis
• B. Microscopic polyangiitis
• C. Churg-Strauss syndrome
• D. Henoch-Schonlein purpura

Answer: (B)

Small-vessel necrotizing vasculitis of capillaries, arterioles, and small venules is most characteristic of microscopic polyangiitis. This disease typically shows a pauci-immune pattern, meaning little or no immune deposition on immunofluorescence, and many patients have ANCA positivity (often p-ANCA/MPO-ANCA). Clinically it can involve the kidneys with rapidly progressive glomerulonephritis and the lungs with capillaritis or hemorrhage, but it lacks the granulomatous inflammation seen in other vasculitides.

Wegener (GPA) features granulomatous inflammation, particularly in the respiratory tract, and is usually c-ANCA/PR3-ANCA positive. Churg-Strauss (EGPA) involves asthma and eosinophilia with granulomatous inflammation and eosinophilic features. Henoch-Schonlein purpura is an IgA immune complex vasculitis, often with palpable purpura and GI/kidney involvement, driven by immune complex deposition rather than a pauci-immune necrotizing process.