A 7-year-old boy presents with multiple recurrent non-blanching purpuric lesions distributed symmetrically over his buttocks and lower extremities, bilateral knee arthralgias, and crampy abdominal pain. Platelet count is normal (280,000/microL), and coagulation profile is normal. What small-vessel vasculitis is this?

Answer and explanation

Correct answer: A. Henoch-Schonlein purpura (IgA vasculitis)

  1. Step 1: Henoch-Schonlein purpura is an IgA immune complex-mediated leukocytoclastic vasculitis.
  2. Step 2: The hallmark presentation is palpable purpura on dependent lower extremities with normal platelet count, often accompanied by arthritis, GI pain, and hematuria.
Answer
Henoch-Schonlein purpura (IgA vasculitis).
Why not the others: 'Immune thrombocytopenic purpura (ITP)' presents with petechiae and purpura caused by profound thrombocytopenia (< 20,000/microL); 'Thrombotic thrombocytopenic purpura (TTP)' is rare in children and presents with microangiopathic hemolysis, severe thrombocytopenia, fever, and neurological deficits; 'Granulomatosis with polyangiitis (GPA)' features c-ANCA positivity with upper and lower respiratory necrotizing granulomas.

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