Sudden unexpected death in GEFS+ families with sodium channel pathogenic variants.

We aimed to describe families with genetic epilepsy with febrile seizures plus (GEFS+) in which individuals suffered sudden unexpected death. The Epilepsy Pharmacogenomics Research Database was reviewed for GEFS + families in which at least one individual had suffered sudden death, and two families were identified. In Family A, five males had febrile seizures and one girl had febrile seizures plus. The latter died at 22 months of age and was classified as definite SUDEP. Molecular genetic testing identified a pathogenic SCN1B variant. In Family B, two brothers had recurrent focal status epilepticus with fever, and were classified as having atypical multifocal Dravet syndrome. The elder brother died suddenly at seven years of age, but was not classified SUDEP because the event occurred following status epilepticus. SCN1A sequencing in the surviving brother identified a likely pathogenic variant. These two cases of sudden death in GEFS + families with likely pathogenic variants in sodium channel genes demonstrate that sudden death may occur in GEFS+, even with mild phenotypes. The presence of sodium channel variants may have further increased the sudden death risk, particularly in the case of SCN1B, a gene which has also been associated with cardiac conditions including Brugada syndrome and long QT.