Possible genetic anticipation in families with idiopathic generalised epilepsy.

Idiopathic generalised epilepsies (IGE) constitute nearly one third of all epilepsies. IGEs manifest with absences, myoclonic jerks and generalised tonic-clonic seizures (GTCS), either alone or in varying combinations, and have a strong genetic background. We present two three-generation families with juvenile myoclonic epilepsy (JME) probands and other affected family members with different forms of IGE in whom genetic anticipation was possible, i.e. the progressive decrease in age at onset with each successive generation. In the first family, the proband presented with JME with all three seizure types with an age at onset of eight years. Her cousin presented with both absence seizures and myoclonic jerks simultaneously at age 14 years, and GTCS occurred one year later. The proband's mother had her first seizures at the age of 39 years (brief myoclonic jerks and subtle absences predated GTCS by a few months). In the second family, the proband and his younger brother presented with JME at the age of 13 years, their mother experienced a single GTCS at the age of 38 years, while the grand-mother died during de novo generalised status at the age of 62 years. To our knowledge, this is one of the few reports to describe the occurrence of possible genetic anticipation in IGE which should be further investigated in larger cohorts of patients.