Henoch–Schönlein purpura (HSP) is the commonest vasculitis of childhood. The first description of this disorder was probably that of a young boy with “bloody points” over the shins of his legs, abdominal pain, blood in the stools and urine and painful subcutaneous oedema, described by William Heberden in 1801. In 1837 Johann Schönlein described the association of purpura and joint pain as “Peliosis rheumatica”. Eduard Henoch, Schönlein’s former student, noted gastrointestinal involvement in association with purpura and arthritis in 1868 and subsequently he recorded renal involvement too.1

DIAGNOSIS

Until recently the 1990 American College of Rheumatology criteria for HSP were the most commonly used criteria for diagnosis.2 This classification was modified but has now been superseded by the European League Against Rheumatism (EULAR) and Paediatric Rheumatology European Society (PReS) consensus criteria for the classification of childhood vasculitis. The group reached consensus that the classification of HSP should be the finding of palpable purpura in the presence of one of either diffuse abdominal pain, a biopsy showing predominant IgA deposition, arthritis or arthralgia and/or renal involvement (any haematuria and/or proteinuria) (table 1).3

EPIDEMIOLOGY

Henoch–Schönlein purpura is found in all age groups, from the age of a few months to late adulthood but it is more common in young children, with over 50% under 5 years and over 75% under 10 years. The clinical features of HSP are often atypical at extremes of age and the illness is more severe in adults while children under 2 years old are less likely than older children to have nephritis or abdominal complications. The reported incidence of HSP varies from 10–20.4 per 100 000 children.4^–7 It is highest in younger children with 22.1/100 000 in the under 14 years and 70.3/100 000 in the 4–7 year age group being reported in one series …