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 f amilies with several cases of idiopathic epilepsy, collected as part o f the Study on the Genetics of Epilepsy of the Italian League against Epilepsy (LICE). The studied families had at least three members affec ted by an idiopathic form of epilepsy in one or more generations. Seve nty-four families (with a total of 2% affected members) have been anal yzed: two families had cases with benign neonatal familial convulsions (BNFC); in 25% of the remaining families all members were affected by the same clinical form, 13.9% had a prevalent clinical form with only one affected member with a different seizure type, 36.1% had two clin ical forms, and 25% had three forms of epilepsy in the same family. Th ere are no clinical differences in the form of epilepsy between the fa milies concordant for one clinical form and families with two or three clinical forms of idiopathic epilepsies. The distribution of the clin ical form in the affected relatives in our families showed the higher concordance with the proband in febrile convulsions (FC, 70.8%) and in epilepsy with generalized tonic-clonic seizures (EGTC, 63.0%). FC and EGTC were highly diffused in the affected relatives in the families w ith other forms of idiopathic epilepsy, above all in the more distantl y related affected family members. In our families we observed a rare association between childhood absence epilepsy (CAE) and juvenile myoc lonic epilepsy (JME). 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 concordanc e was less evident and there was a tendency toward a different phenoty pic expression.