Henoch-Schönlein purpura (HSP) is an IgA-mediated, autoimmune, hypersensitivity vasculitis of childhood. The main clinical features are skin purpura, arthritis, abdominal pain, gastrointestinal bleeding, orchitis and nephritis. The aetiology remains unknown.

Epidemiology

• In the United Kingdom, the estimated annual incidence is 20 cases per 100,000 population.¹
• The peak prevalence is in children aged 3-10 years. It is rare in infants and young children.
• The male-to-female ratio is 1.5-2:1. Whites are more affected than blacks.

Risk factors

Associated conditions preceding HSP include:

• Infections: for example, Group A streptococci, mycoplasma, Epstein-Barr virus
• Vaccinations
• Environmental exposures: for example, drug and food allergens, pesticides, cold exposure, insect bites²

Presentation

• The disease occurs mostly in the winter months. About 50% of patients have a preceding upper respiratory tract infection (URTI).³
• Generally, patients appear to be mildly ill, with low-grade fever.
• Symmetrical erythematous macular rash, especially on the back of the legs, buttocks and ulnar side of the arms.
• Within 24 hours, the macules evolve into purpuric lesions, which may coalesce and resemble bruises.
• Abdominal pain and bloody diarrhoea may precede the typical purpuric rash. Intussusception should then be considered (occurs in 2-3% of patients). HSP may also cause nausea and vomiting.
• Joint pain, especially knees and ankles. Joints may also be swollen and tender but permanent deformity does not occur.
• Renal involvement:
  • Affects 50% of older children and 25% of children under 2 years of age.
  • Less than 1% of patients progress to end stage renal disease.
  • Usually occurs within 3 months of disease onset.
  • There is usually no relationship between the severity of nephritis and the extent of the other manifestations of HSP.
  • Microscopic haematuria with mild-to-moderate proteinuria may occur.
  • Nephrotic syndrome may also occur.
  • Oliguria and hypertension are rare.
• Scrotal involvement may mimic testicular torsion.
• Neurological: headaches may occur.

Differential diagnosis

• Connective tissue diseases, e.g. systemic lupus erythematosus (SLE)
• Other causes of purpuric rash, e.g. thrombocytopenia
• Other causes of glomerulonephritis
• Acute haemorrhagic oedema of infancy is milder and occurs in infants younger than 2 years. The onset is sudden, with acute purpura, bruises and tender oedema of the limbs and face.⁴

Investigations

Diagnosis of HSP is clinical and not based on laboratory investigations.³ The following abnormalities may be present:

• Urinalysis: haematuria and/or proteinuria are present in 10-20% of patients.³
• FBC: may be raised white cell count with eosinophilia; normal or increased platelets
• Raised ESR
• Serum creatinine may be elevated in renal involvement
• Serum IgA levels are often increased
• Autoantibody screen: connective tissue diseases
• Abdominal ultrasound: if gastrointestinal symptoms - for diagnosis of intestinal obstruction
• Barium enema: may be used to confirm and treat intussusception
• Testicular ultrasound: assessment of possible torsion
• Renal biopsy: if persistent nephrotic syndrome

Management

• HSP is usually self-limiting and no form of therapy has been shown appreciably to shorten the duration of disease or prevent complications. Therefore treatment for most patients remains primarily supportive.
• Non-steroidal anti-inflammatory drugs may help joint pain but should be used with caution in patients with renal insufficiency.
• May require admission to hospital for monitoring of abdominal and renal complications.
• Nephropathy: treated supportively. A variety of drugs (steroids, azathioprine, cyclophosphamide) and plasmapheresis have been used to prevent the progression of the renal disease but the results of trials have been inconsistent.⁵
• Corticosteroids can ameliorate associated arthralgias and the symptoms associated with gastrointestinal dysfunction. There was no evidence of benefit of prednisone in preventing serious long-term kidney disease in HSP.⁶
• No controlled clinical trials have been performed with immunosuppressive drugs, although azathioprine or cyclophosphamide may be beneficial.⁵
• Plasma exchange is used in the management of some adults with vasculitis and idiopathic rapidly progressive nephritis.⁵

Complications

• Renal involvement occurs in 50% of older children but is only serious in approximately 10% of patients. Less than 1% of patients with HSP progress to end-stage renal failure.³ The renal prognosis is worse in older children and adults.
• Monitoring for renal involvement:⁷
  • A review found that no long-term renal impairment occurred after normal urinalysis.
  • If urinalysis is normal at presentation, the review recommends that testing should be continued for six months.
  • There is no need to follow up after the first six months those whose urinalysis remains normal.
• Other rare complications include myocardial infarction, pulmonary haemorrhage, pleural effusion, intussusception (in 2-3% of patients), gastrointestinal bleeding, bowel infarction, seizures and mononeuropathies.
• Recurrence of symptoms may occur. Recurrence of renal impairment may also occur but is rare.

Prognosis

• HSP is an acute self-limited illness and usually resolves without treatment, but may rarely lead to complications. Initial attacks of HSP can last several months. One third of patients have one or more recurrences.
• Children younger than 3 years have a shorter, milder course and fewer recurrences.
• The long-term prognosis of HSP is directly dependent on the severity of renal involvement.⁸