Narcolepsy in a 2-year-old boy.

This report describes the prospective follow-up of a 2-year-old child with narcolepsy. The initial clinical diagnosis was confirmed by the onset of cataplexy when the child was 5 years old. He does not have the HLA genotype characteristic of narcolepsy or an identifiable brain lesion, although he has megalencephaly and mild learning difficulties. Treatment with dietary tyrosine supplements who are to young to use stimulants safely. The morbidity of narcolepsy is high and early diagnosis is therefore important, as treatment is effective.