An 8-year-old boy develops palpable purpura over the buttocks and lower limbs, colicky abdominal pain, and knee arthralgia two weeks after an upper respiratory infection. Urinalysis shows microscopic hematuria. Skin biopsy shows leukocytoclastic vasculitis. Direct immunofluorescence of the skin biopsy will demonstrate:

• A Granular IgA and C3 deposition in vessel walls ✓
• B Linear IgG along the basement membrane
• C Paucity of immunoglobulin deposition (pauci-immune pattern)
• D Intercellular IgG in a fishnet pattern

Explanation

Henoch-Schonlein purpura (IgA vasculitis) is a small-vessel leukocytoclastic vasculitis driven by IgA-containing immune complexes, often triggered by mucosal infections in children. Immunofluorescence shows granular IgA with C3 in affected vessel walls, and the same deposits appear in renal glomeruli when nephritis occurs. A pauci-immune pattern suggests ANCA-associated vasculitis instead, and linear IgG indicates anti-GBM disease.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.