HSP — Viva

Q1: Definition and significance (2 min)

What is Henoch-Schonlein purpura, and why is it the most important childhood vasculitis? HSP (now IgA vasculitis) is a small-vessel leukocytoclastic vasculitis caused by deposition of galactose-deficient IgA1 immune complexes in skin, gut, joints and glomeruli. It is the most common vasculitis of childhood (~10-20/100,000/year). It matters because it is common, often self-limiting, but carries the risk of intussusception and a small but real risk of end-stage renal disease (1-2%) from late nephritis. The molecular biology is identical to IgA nephropathy (Berger disease) — HSP is the systemic form.

Q2: The tetrad and the discriminator (2 min)

Describe the classic clinical tetrad and the single bedside discriminator from ITP. Tetrad: (1) palpable non-blanching purpura on dependent areas (lower limbs, buttocks) — mandatory; (2) arthritis/arthralgia of knees and ankles (periarticular, non-erosive); (3) colicky abdominal pain (risk of ileo-ileal intussusception); (4) renal involvement (haematuria/proteinuria). Discriminator: the PLATELET COUNT IS NORMAL in HSP (the purpura is vasculitic); in ITP platelets are low and the purpura is non-palpable.

Q3: Classification criteria (3 min)

Reproduce the EULAR/PRINTO/PRES 2010 criteria and contrast with the 1990 ACR criteria. EULAR/PRINTO/PRES 2010 (current paediatric standard): mandatory purpura/petechiae with lower-limb predominance PLUS at least one of (a) diffuse abdominal pain, (b) IgA deposition on biopsy, (c) arthritis/arthralgia, (d) renal involvement (any haematuria/proteinuria). Sensitivity ~100%, specificity ~87%. 1990 ACR: 2 of 5 — age under 20, palpable purpura, acute abdominal pain, biopsy with granulocytes in small-vessel walls, arthritis. ACR criteria were designed for mixed adult/paediatric cohorts and are less accurate in children.

Q4: Pathophysiology (3 min)

Walk through the molecular cascade of HSP. Galactose-deficient IgA1 (aberrant hinge-region O-glycosylation) -> anti-glycan IgG/IgA autoantibodies -> large circulating immune complexes -> deposition in the glomerular mesangium and walls of small vessels (skin, gut, joints, testis) -> activation of the ALTERNATIVE and LECTIN complement pathways (IgA does NOT activate classical) -> C3a, C5a, MAC (C5b-9) -> neutrophil chemotaxis -> fibrinoid necrosis, nuclear dust (leukocytoclastic vasculitis). Result: palpable purpura, GI oedema/bleeding, periarticular swelling, crescentic glomerulonephritis.

Q5: Management and the role of steroids (3 min)

Outline management and explain when steroids are — and are not — indicated. Most cases: supportive (rest, hydration, paracetamol). NSAIDs (ibuprofen 5-10 mg/kg TDS) for arthritis IF renal function is normal — avoid NSAIDs if renal involvement. Corticosteroids (oral prednisolone 1-2 mg/kg/day; IV methylprednisolone pulses for severe disease) for severe GI pain/bleeding, significant renal involvement, severe systemic symptoms, or scrotal involvement. CRITICAL: steroids do NOT prevent nephritis (Jauhola 2011) — do NOT give prophylactically. HSP nephritis ISKDC III-VI: add cyclophosphamide/MMF/calcineurin/rituximab and ACE inhibitor (enalapril) for proteinuria.

Q6: Complications, pitfalls and follow-up (3 min)

What complications must you exclude, and what is the follow-up plan? GI: intussusception (ILEO-ILEAL — usually needs surgery, not enema), GI bleed, protein-losing enteropathy. Renal: HSP nephritis, nephritic/nephrotic syndrome, crescentic RPGN, CKD/ESRD. Surgical: testicular torsion (scrotal HSP). Neurological (rare): PRES, seizures, intracranial bleed. Pitfalls: missing meningococcaemia (sick child, rapidly progressive, non-dependent purpura), missing intussusception, missing late nephritis by not following up, giving steroids to prevent nephritis, using NSAIDs with renal involvement. Follow-up: blood pressure and urinalysis weekly during active disease, then monthly for 6 months, then every 3-6 months to 12 months (longer if renal involvement) — because nephritis develops late and determines prognosis.