In microscopic polyangiitis, segmental fibrinoid necrosis involves which layer of the arterial wall?

In microscopic polyangiitis, segmental fibrinoid necrosis involves which layer of the arterial wall?

• A. Media
• B. Intima
• C. Adventitia
• D. Elastic lamina

Answer: (A)

Microscopic polyangiitis shows necrotizing vasculitis of small to medium vessels with fibrinoid necrosis most prominently in the tunica media of arteries. The media houses smooth muscle, and inflammatory destruction here leads to the pink, fibrinoid deposits seen as fibrinoid necrosis on microscopy. The disease is pauci-immune and ANCA-associated, so the damage is driven by neutrophil activation rather than immune complex deposition, focusing the destructive process in the medial layer. The intima and adventitia can be involved in some lesions, but the characteristic fibrinoid necrosis centers on the media, while the elastic lamina is not the primary site of this necrosis.

Microscopic polyangiitis shows necrotizing vasculitis of small to medium vessels with fibrinoid necrosis most prominently in the tunica media of arteries. The media houses smooth muscle, and inflammatory destruction here leads to the pink, fibrinoid deposits seen as fibrinoid necrosis on microscopy. The disease is pauci-immune and ANCA-associated, so the damage is driven by neutrophil activation rather than immune complex deposition, focusing the destructive process in the medial layer. The intima and adventitia can be involved in some lesions, but the characteristic fibrinoid necrosis centers on the media, while the elastic lamina is not the primary site of this necrosis.