PHENOTYPIC-EXPRESSION OF BENIGN FAMILIAL NEONATAL CONVULSIONS LINKED TO CHROMOSOME-20

Objectives: To determine whether the syndrome of benign familial neona tal convulsions in a large family was linked to markers on chromosome 20q and to study the seizure patterns in affected individuals. Design: A clinical and molecular biologic study of a single large family in w hich the probands were identical twins with benign familial neonatal c onvulsions. Patients: Thirteen living affected family members and 27 l iving unaffected family members were evaluated. Results: Multipoint li nkage analysis with use of the chromosome 20q markers CMM6 and RMR6 ga ve a maximum lod score of 3.13 at theta=0.063, indicating linkage in t his family. Of the 13 affected members, 10 had known neonatal seizures . Four subjects had febrile seizures, of whom only two had known neona tal seizures. Two members had afebrile seizures later, one of whom had not previously suffered neonatal or febrile seizures. Conclusion: The phenotypic heterogeneity in this family, with an epilepsy syndrome de termined by a single gene, was striking. This suggests that molecular genetic approaches to the common forms of idiopathic epilepsy, involvi ng patients with clinically similar phenotypes from unrelated families , may be inappropriate.