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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- IgA vasculitis (now the preferred name) — most common vasculitis in children. Peak age 3–10 years
- Classic tetrad: palpable purpura (non-thrombocytopenic, buttocks and extensor surfaces of legs), arthralgia/arthritis, abdominal pain (colicky), renal involvement (haematuria, proteinuria)
- Usually self-limiting over 4–6 weeks. Rash may be recurrent
- Renal involvement (HSP nephritis) occurs in ~30–50% — ranges from microscopic haematuria to nephrotic/nephritic syndrome
- All children need urine monitoring (dipstick for blood and protein) weekly for first month then monthly for 6–12 months — renal involvement may develop late
- Management: supportive (analgesia, rest). Steroids may help severe abdominal pain. Refer to nephrology if significant renal involvement
Overview
Henoch-Schönlein purpura (IgA vasculitis) is a systemic small-vessel vasculitis caused by IgA immune complex deposition in vessel walls. It predominantly affects children and is characterised by palpable purpura (typically over the buttocks and lower limbs), joint pain, abdominal pain, and renal involvement. The condition is usually triggered by a preceding upper respiratory tract infection. It is generally self-limiting but renal involvement (which may be delayed) is the main determinant of long-term outcome.
Epidemiology
HSP is the most common vasculitis in childhood. Incidence is approximately 20 per 100,000 children per year. Peak age 3–10 years, with 90% of cases in children. Male:female ratio ~1.5:1. More common in autumn and winter. Typically preceded by URTI (1–3 weeks before). Group A streptococcus, Mycoplasma, and EBV have been implicated as triggers.
Clinical Features
Symptoms
Palpable purpuric rash — non-blanching, typically over buttocks and extensor surfaces of lower limbs. May be preceded by urticaria
Arthralgia or arthritis — large joints (knees, ankles), often periarticular swelling. Non-deforming, self-limiting
Abdominal pain — colicky, may be severe. Can precede rash (diagnostic challenge)
Bloody stools or melaena (GI vasculitis)
Scrotal swelling and pain (can mimic testicular torsion)
Haematuria (visible or microscopic) — indicates renal involvement
Signs
Palpable purpura — raised, non-thrombocytopenic, symmetrically distributed on gravity-dependent areas
Joint swelling without deformity
Abdominal tenderness
Hypertension (renal involvement)
Oedema (nephrotic syndrome component)
Investigations
First-line
UrinalysisDipstick for blood and protein at presentation and regular follow-up. uPCR if proteinuria detected
Blood pressureMonitor regularly — hypertension indicates renal involvement
FBC and coagulationNormal platelet count (differentiates from thrombocytopenic causes of purpura). Normal clotting
Second-line
U&Es, creatinine, albuminAssess renal function and proteinuria severity
Serum IgAElevated in ~50% — supportive but not diagnostic
Complement (C3, C4)Normal (differentiates from lupus and MPGN)
Specialist
Renal biopsyIf severe or progressive renal involvement (nephrotic/nephritic syndrome, declining renal function). Shows IgA mesangial deposits (identical to IgA nephropathy)
1
Supportive care
- Analgesia: paracetamol and ibuprofen (NSAIDs safe unless significant renal involvement)
- Rest during acute phase
- Most cases resolve spontaneously within 4–6 weeks
2
Severe disease
- Severe abdominal pain: consider short course of prednisolone 1–2 mg/kg/day — may reduce GI symptoms but does NOT prevent renal disease
- Intussusception: can complicate HSP (typically ileocolic) — USS if severe abdominal pain with mass/obstruction
- Scrotal involvement: USS to exclude testicular torsion
3
Renal monitoring (CRITICAL)
- Urine dipstick weekly for first month, then monthly for 6–12 months
- Blood pressure at each review
- If persistent proteinuria or haematuria: refer to paediatric nephrology
- If nephrotic or nephritic syndrome: renal biopsy and immunosuppressive treatment
Complications
- HSP nephritis: Occurs in 30–50%. Usually mild (microscopic haematuria). 5–10% develop significant renal impairment. Rarely progresses to CKD/ESRD
- Intussusception: Typically ileocolic (vs ileocaecal in idiopathic) — bowel wall haematoma acts as lead point
- GI haemorrhage: From mucosal vasculitis — usually self-limiting
- Recurrence: ~30% have recurrent episodes, usually milder
UKMLA Exam Tips
- 1Palpable purpura + normal platelets + arthralgia + abdominal pain in a child = HSP
- 2Platelets are NORMAL — this differentiates from ITP (low platelets) and meningococcal disease (unwell child)
- 3Renal involvement may develop LATE — monitor urine for 6–12 months after diagnosis
- 4Abdominal pain can precede the rash — diagnostic challenge (can mimic surgical abdomen)
- 5Intussusception complicating HSP is typically ILEO-ILEAL (not ileocaecal)
- 6IgA deposits on renal biopsy are identical to IgA nephropathy — considered the same disease spectrum
practicetest your knowledge on henoch-schönlein purpuraApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — paediatrics and beyond.
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