Clinical genetic study in juvenile myoclonic epilepsy

PURPOSE To evaluate clinical features of probands with juvenile myoclonic epilepsy (JME) and affected members of their families in order to study clinical genetics of JME. METHOD Thirteen unrelated families with at least two members with history of seizures were identified; clinical and genealogic data were collected from JME probands and family members. RESULTS All probands had myoclonic and generalized tonic-clonic seizures (GTCS), while absences occurred in 25% of them. The average age of seizure onset was 13 years. Totally 22 members from 13 families had history of seizures with average age of seizure onset at 18 years. Ten family members had JME, three had epilepsy with GTCS, two had juvenile absence epilepsy, one had adult onset myoclonic epilepsy and six of the affected individuals had unclassified type of epilepsy. In five families, JME was the solely clinical feature. JME dominated among siblings, while phenotypic heterogeneity was observed in second and third degree relatives. In three multi-generation families, members with adult onset genetic generalized epilepsies (GGE) were identified. CONCLUSION We found phenotypic heterogeneity regarding epilepsy type and age of seizure onset. Using pedigree analysis, we found no evidence for preferential maternal or any other distinctive inheritance pattern. Further study is needed to confirm and clarify the results.