Which disease is best described as a hypersensitivity vasculitis affecting capillaries, arterioles, and small venules?

• A. Kawasaki disease
• B. Wegener granulomatosis
• C. Microscopic polyangiitis
• D. Churg-Strauss Syndrome

Answer: (C)

Small-vessel necrotizing vasculitis with little to no immune complex deposition best fits microscopic polyangiitis. This disease targets the smallest vessels—capillaries, arterioles, and small venules—producing a pauci-immune, necrotizing vasculitis. It commonly presents with kidney involvement such as rapidly progressive glomerulonephritis and can cause pulmonary hemorrhage, and it is often associated with MPO-ANCA (p-ANCA).

Kawasaki disease is a medium-vessel vasculitis seen mainly in children and involves larger arteries like the coronaries. Granulomatosis with polyangiitis (Wegener) shows granulomatous inflammation with necrotizing vasculitis, typically affecting the respiratory tract and kidneys and often associated with c-ANCA (PR3-ANCA). Churg-Strauss (eosinophilic granulomatosis with polyangiitis) features eosinophilic granulomatous inflammation and is associated with asthma and eosinophilia. The pattern of involvement described—capillaries, arterioles, and small venules with a pauci-immune profile—is most characteristic of microscopic polyangiitis.