An 8-year-old boy develops palpable purpura over the buttocks and lower limbs with colicky abdominal pain after an upper respiratory infection. Skin biopsy shows leukocytoclastic vasculitis. On direct immunofluorescence, the deposit expected in the vessel walls is:

• A Granular IgA and C3 ✓
• B Linear IgG along the vessel wall
• C Fibrinogen alone without immunoglobulin
• D Intercellular IgM in the epidermis

Explanation

Henoch-Schonlein purpura is an IgA immune complex small-vessel vasculitis. DIF of involved skin shows granular IgA (with C3) deposited in postcapillary venules, distinguishing it from other leukocytoclastic vasculitides where IgG or IgM may dominate. Fibrin and fibrinogen are present in any necrotizing vasculitis as part of fibrinoid necrosis, but isolated fibrinogen without immunoglobulin does not define HSP.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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