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Histology: non‐granulomatous small‐vessel leukocytoclastic vasculitis.
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Immune deposits:
- vessel wall deposition of complement C3 occurs in two‐thirds of the cases;
- Deposition of Immunoglobulin M, immunoglobulin A (≈30%), immunoglobulin G or immunoglobulin E is less common.
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Contrary to Henoch-Schönlein vasculitis, deposition of immunoglobulin A occurs exclusively in a minority of cases.
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Acute hemorrhagic edema of young children is a distinctive immune‐mediated vasculitis (contrary to pauci‐immune vasculitides such as microscopic polyangiitis, granulomatosis with polyangiitis, and eosinophilic granulomatosis with polyangiitis).
