Henoch-Schönlein purpura.

Henoch-Schönlein purpura (HSP) is the most common vasculitic disease of childhood. It is a multisystem disease most commonly aVecting skin, joints, gastrointestinal tract, and kidneys, but other organs may be aVected. Epidemiological studies have shown HSP to have an annual incidence of approximately 13.5–18/ 100 000 children. 2 Although this is a condition that can occur from age 6 months to adulthood, 50% of cases occur in children under 5 years of age and 75% are under 10 years. In most reports HSP is more common in boys. The cause remains unknown although there is often an antecedent respiratory infection. Streptococcal infections have been implicated but other organisms including adenovirus, parvovirus, and mycoplasma have also been reported to precede HSP. The increased incidence in winter and spring supports an infectious trigger in a susceptible individual. The American College of Rheumatology 1990 criteria for the classification of HSP aimed to identify diagnostic criteria to diVerentiate HSP from other vasculitic diseases. The four criteria identified, of which two are necessary to make the diagnosis, are: + age < 20 years at onset + palpable purpura + “bowel angina” (diVuse abdominal pain or bowel ischaemia usually with bloody diarrhoea) + biopsy evidence of granulocytes in the walls of arterioles or venules. The diagnosis is usually made after the appearance of the classic rash that primarily aVects the extensor surfaces and may be urticarial or purpuric. Joint involvement occurs in 60–84% of cases and generally aVects the ankles and knees. It is often the most incapacitating part of the initial illness. Gastrointestinal disease occurs in up to 76% of patients varying from colicky abdominal pain, nausea, and vomiting to intestinal haemorrhage, intussusception, pancreatitis, and hydrops of the gall bladder. There is an increased risk of renal disease in those with bloody stools. The reported incidence of renal disease ranges from 20–100%. In 80% of those with renal involvement it becomes apparent within the first four weeks of the illness. The remainder predominantly occurs over the next two months although a few are further delayed. Haematuria with or without proteinuria is the most common renal feature. Acute nephritic syndrome may be associated with renal insuYciency, nephrotic syndrome, or both. Hypertension may be associated with acute nephritis but has also been reported in the absence of urinary abnormality. Florid cerebral manifestations including seizures, paresis or coma are uncommon but have been reported. It has been suggested that mild cerebral involvement presenting as headaches may occur in as many as a third of cases, and this may coincide with electroencephalogram abnormalities. Scrotal involvement is not uncommon and occasionally resembles testicular torsion, which must be excluded. Other rare manifestations are cholecystitis and myocardial infarction. Interstitial lung disease with impairment of lung diVusion capacity has been reported, although this was clinically insignificant.