Histology of a palpable purpuric lesion shows fibrinoid necrosis of vessel walls surrounded by neutrophils with fragmentation of their nuclei (leukocytoclasia) and extravasated red blood cells. Which segment of the vascular tree is characteristically affected in this process?

• A Subcutaneous muscular arteries
• B Arterioles of the deep dermal plexus
• C Capillary loops of the dermal papillae
• D Postcapillary venules of the upper dermis ✓

Explanation

Cutaneous leukocytoclastic (hypersensitivity) vasculitis is a small-vessel vasculitis centred on postcapillary venules in the upper dermis, where immune complex deposition triggers complement activation, neutrophil chemotaxis, karyorrhexis and fibrinoid necrosis. Arterioles and muscular arteries are targets of medium-vessel diseases such as polyarteritis nodosa, and papillary capillary involvement alone does not constitute a necrotising vasculitis.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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