Polyarteritis nodosa (PAN) is a necrotizing vasculitis that affects which type of vessels and typically spares which organ?

• A Small vessels including capillaries and venules; affects the lungs
• B Large elastic arteries; spares the kidneys
• C Medium-sized muscular arteries; spares the lungs ✓
• D Arterioles and glomerular capillaries; involves the skin exclusively

Explanation

PAN is a systemic necrotizing vasculitis of medium-sized muscular arteries that characteristically spares the pulmonary circulation — an important distinguishing feature from ANCA-associated vasculitides (GPA, EGPA, MPA) which frequently involve pulmonary vessels and cause pulmonary hemorrhage or capillaritis. PAN causes aneurysmal dilatations of renal, mesenteric, and hepatic arteries, and is associated with hepatitis B in about 30% of cases. ANCA is typically negative. Microscopic polyangiitis (MPA) is the small-vessel counterpart that does affect the lungs.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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