Concordance of clinical forms of epilepsy in families with several affected members

Evidence for genetic heterogeneity in epilepsy is strong. We evaluated the concordance of clinical forms in the same family in a series of family with several cases of idiopathic epilepsy. The studied family had at least three members affected by an idiopathic form of epilepsy in one or more geneations. Seventy-four families have been analyzed; two families had cas es with benign neonatal familial convulsions; in 25% of the remaining families all members were affected by the same clinical form. There are no clinical differences in the form of epilepsy between the families concordant for one clinical form and families with two or three clinical forms of idiopathic epilepsies. In every idiopathic form of epilepsy, there was a high concordance for the seizure phenotype in first-degree affected relatives, whereas in more distantly related family members concordance was less evident abd there was a tendency toward a different phenotypic expression.