Incidence of Henoch-Schönlein purpura, Kawasaki disease, and rare vasculitides in children of different ethnic origins.

BACKGROUND: The frequency and ethnic variation of Henoch-Schönlein purpura, Kawasaki disease, and rarer vasculitides during childhood are not well characterised. Our aim was to ascertain the incidence and ethnic distribution of these conditions in children resident in a region of the UK with a diverse ethnic mix.

METHODS: 1.1 million children younger than age 17 years live in the West Midlands. Between Sept 1, 1996, and Aug 31, 1999, we surveyed this population with monthly questionnaires sent to 321 consultants, a single questionnaire sent to 2860 family doctors, and review of 406 case notes with diagnostic codes for vasculitis. We included in the analyses children who fulfilled established criteria for vasculitis with disease onset during the study, and calculated incidence rates from population rates derived from the census of 1991.

FINDINGS: We identified 586 new instances of vasculitis and connective tissue disease. The estimated annual incidence of Henoch-Schönlein purpura was 20.4 per 100000, and was highest between the ages of 4 years and 6 years (70.3 per 100000). The estimated annual incidence of Kawasaki disease was 5.5 per 100000 in children younger than 5 years, and was highest in Indian subcontinent Asian children (14.6 per 100000). Indian subcontinent Asian and black children had the highest incidence of systemic lupus erythematosus, juvenile dermatomyositis, and other primary systemic vasculitides.

INTERPRETATION: Childhood Henoch-Schönlein purpura is more frequent in the West Midlands than previously reported, and Kawasaki disease has a higher incidence than previously indicated in the UK, with the highest incidence in Indian subcontinental Asian children. Other vasculitis is rare in childhood.