A 7-year-old boy develops palpable purpura over the buttocks and legs, colicky abdominal pain, and knee arthralgia two weeks after an upper respiratory infection. Urinalysis shows microscopic hematuria. Skin biopsy of a purpuric lesion would most likely show:

• A Thrombosis of dermal vessels with platelet-rich thrombi and no inflammation
• B Granulomatous inflammation with eosinophils around small vessels
• C Leukocytoclastic vasculitis with IgA deposition in vessel walls on immunofluorescence ✓
• D Necrotizing vasculitis of deep dermal arteries with fibrinoid necrosis and aneurysm formation

Explanation

This is Henoch-Schonlein purpura (IgA vasculitis), the commonest systemic vasculitis of childhood, typically following an upper respiratory infection. It affects small vessels of skin, gut, joints, and kidneys, and biopsy shows leukocytoclastic vasculitis with IgA immune complex deposition in vessel walls, distinguishing it from other small-vessel vasculitides. Eosinophilic granulomatous inflammation suggests EGPA, platelet thrombi without inflammation suggest thrombotic thrombocytopenic purpura, and deep arterial fibrinoid necrosis with aneurysms suggests polyarteritis nodosa.

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.