Genetic epidemiology of epilepsy: a twin study.

The study explored the genetic susceptibility and prevalence of epilepsy in twins. The data on epilepsy were retrieved from the health records of 199 pairs of twins. Proband concordance rate in monozygotic (MZ) twins was four times more than that in dizygotic (DZ) twins (0.67 vs. 0.17). Three of 15 (20%) affected twin kinships had epileptic first-degree relatives. These findings indicated significant underlying genetic susceptibility to epilepsy with the Holzinger's heritability estimate being 0.45. The prevalence of epilepsy was similar in MZ (45.45), DZ (45.11) twins, and their non-twin siblings (47.60). In the general population from various nationalities, the mean prevalence rate of epilepsy varied from 5 to 17 per 1000. The appreciably higher prevalence rate in twin kinships could be attributed to peculiar development factors associated with the twinning process or the intrauterine environment of mothers having tendencies to bear twins. Of the genetic markers, PTC locus seemed to be associated with the susceptibility to epilepsy. The allele frequency of non-tasters (t) seemed greater in epileptic twin kinships (0.71) than that in the general population (0.53). The frequency of non-tasters was similar in MZ and DZ twins and singletons: 27.3%, 26%, and 27.7% respectively. The PTC data on the general population was based on a sample of 278 individuals.