Juvenile myoclonic epilepsy: an autosomal recessive disease.

We undertook genetic study of patients with juvenile myoclonic epilepsy (JME) from 17 families. There was a mean of 8 children in each sibship. Siblings were affected in 8 sibships, and some families had more than 2 members affected by JME. Half-siblings and parental involvement were found in only 1 sibship each. The segregation ratio was 0.123 but increased to 0.18 with correction for age of onset. Parental consanguinity was found in 9 (45%) of the sibships. The evidence establishes an autosomal recessive mode of inheritance for JME.