Reye's syndrome in children under three years old.

The National Childhood Encephalopathy Study identified 37 cases of Reye's syndrome in children aged between 2 and 36 months in a 3-year period, giving an estimated incidence in Great Britain of 0.7/100 000 children a year. The diagnostic features were neither consistently positive in these cases, nor negative in 11 others later considered not to have Reye's syndrome. The prognosis was poor; the fatality rate was 46%, and 60% of the survivors were handicapped. A surveillance scheme to investigate pathological, clinical, and epidemiological factors in this rare condition is required. This has now been set up in the UK.