Polyarteritis nodosa presents with which histologic feature?

• A. Transmural inflammation with fibrinoid necrosis
• B. Necrotizing granulomas with caseation
• C. Eosinophilic infiltration with granulomas
• D. Immune complex deposition with linear basement membrane

Answer: (A)

Polyarteritis nodosa is a necrotizing vasculitis of medium-sized arteries. The defining histologic feature is transmural inflammation of the vessel wall with fibrinoid necrosis, often leading to aneurysm formation and occlusion. This pattern reflects immune-complex–mediated injury affecting visceral and renal arteries.

Other choices describe different diseases: necrotizing granulomas with caseation are typical of TB or granulomatosis with polyangiitis; eosinophilic infiltration with granulomas points to eosinophilic granulomatosis with polyangiitis; immune complex deposition with a linear basement membrane pattern is characteristic of anti-GBM disease. Thus the transmural inflammation with fibrinoid necrosis best matches polyarteritis nodosa.