An 8-year-old boy presents with palpable purpura over the buttocks and lower limbs, colicky abdominal pain, and arthralgia of knees and ankles. Urinalysis shows microscopic haematuria. Skin biopsy is performed. Which finding on immunofluorescence confirms the diagnosis?

• A Pauci-immune necrotising small vessel inflammation
• B Linear IgG deposition along the basement membrane
• C Granular IgA and C3 deposition in dermal vessels ✓
• D Intercellular IgG deposition in the epidermis

Explanation

IgA vasculitis (Henoch-Schonlein purpura) is a small vessel immune complex vasculitis of children presenting with the classic tetrad of palpable purpura, arthralgia, abdominal pain and renal involvement. Immunofluorescence shows granular IgA and A3 deposits in vessel walls, reflecting IgA1-containing circulating complexes that also deposit in glomeruli. Pauci-immune patterns point instead to ANCA-associated vasculitides such as GPA or MPA.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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