Overview

Henoch–Schönlein purpura (HSP), now termed IgA vasculitis, is the most common systemic vasculitis in children, characterised by IgA1-dominant immune complex deposition in small vessels, particularly affecting the skin, joints, gastrointestinal tract, and kidneys. It predominantly occurs in children aged 3–10 years, with a slight male predominance, and often follows an upper respiratory tract infection. The incidence is approximately 10–30 per 100,000 children per year. The disease is usually self-limiting but can have significant morbidity when renal involvement occurs.

Anatomy and Physiology

• Small vessels: Capillaries, venules, arterioles—sites of immune complex deposition
• IgA function: Mucosal immunity; produced in response to infections
• Complement system: Alternative and lectin pathways activated by immune complexes

Aetiology & Risk Factors

Aetiology

• Post-infectious immune response (most commonly URTI)
• Viral or bacterial triggers
• Immune dysregulation with IgA overproduction

Risk Factors

• Age 3–10 years
• Male sex
• Recent infection
• Seasonal variation (winter/spring)

Pathophysiology

• Trigger (infection) → increased IgA production
• Formation of IgA immune complexes
• Deposition in small vessels
• Complement activation → inflammation
• Vascular damage → purpura, organ involvement

Clinical Manifestations

• Palpable purpura (legs, buttocks)
• Arthralgia/arthritis
• Abdominal pain (colicky)
• GI bleeding
• Haematuria ± proteinuria
• Oedema (hands, feet, scrotum)

Diagnosis

EULAR/PRINTO/PRES Criteria (2008 validated):

• Mandatory: Purpura/petechiae
• Plus ≥1:
  • Abdominal pain
  • Arthritis/arthralgia
  • Renal involvement
  • IgA deposition on biopsy

Investigations

• Urinalysis (haematuria, proteinuria)
• Bloods: CRP, ESR, renal function
• Skin biopsy (IgA deposition) if uncertain
• Imaging (USS abdomen if intussusception suspected)

Differentials

• Meningococcal sepsis
• ITP
• ANCA vasculitis
• SLE

Treatment

Acute management

• Mild pain
  • Paracetamol
  • NSAIDs (if not older)
  • Elevate oedematous lower limb
• Moderate-severe pain
  • Admit
  • IV steroids OR oral steroids
  • Paediatric consult
  • Elevate oedematous lower limb

Ongoing management

• Regular GP/Paediatrician review for progress and complications

Complications & Prognosis

Complications

• Intussusception
• GI bleeding
• Renal disease → CKD
• Recurrence

Prognosis

• Usually self-limiting in children
• Renal involvement determines outcome
• Poor prognostic factors:
  • Persistent proteinuria
  • Hypertension
  • Older age

References

1. Ozen S, et al. EULAR/PRINTO/PRES criteria for IgA vasculitis. Ann Rheum Dis. 2010.
2. Weiss PF. IgA vasculitis. Lancet. 2015.
3. KDIGO Guidelines. Glomerular diseases. 2021.