Henoch-Schönlein purpura (IgA vasculitis)
Overview
Henoch-Schönlein purpura (HSP), now generally termed IgA vasculitis, is an IgA‑mediated, leukocytoclastic small‑vessel vasculitis that classically affects skin, joints, gastrointestinal tract and kidneys. Most cases are paediatric: more than 90% occur in children under 10 years, with a peak at 4-6 years. Adult presentations are less common but carry a higher risk of significant renal disease (RCEM).
Pathogenesis and precipitating factors
Immune‑complex (IgA) deposition in small vessels with local complement activation produces a palpable, non‑blanching purpuric rash and variable inflammation in affected organs. HSP commonly follows an upper respiratory or other infection by days to weeks.
Typical clinical features
- Skin: palpable, non‑blanching purpura most commonly on the buttocks and extensor surfaces of the legs and arms; local dependent oedema is common.
- Joints: transient migratory oligoarthritis or arthralgia, typically affecting knees and ankles; usually non‑erosive.
- Gastrointestinal: colicky abdominal pain, nausea, vomiting and diarrhoea; visible or occult GI bleeding may occur. Severe abdominal pain can indicate intussusception in children.
- Renal: microscopic or macroscopic haematuria and mild-moderate proteinuria; nephritic or nephrotic presentations are less common but possible.
Time course and prognosis
- The rash often appears early; renal involvement usually develops between 1 day and 1 month after symptom onset.
- Most paediatric cases resolve within approximately 4 weeks.