Aims: The purpose of this study is to survey the data from the literature on the subject of the possible genetic origin of severe myoclonic epilepsy in infancy (SMEI).
Development: SMEI must inevitably be included within the phenotype of febrile seizures, which is made up of febrile seizures, febrile seizures plus, generalized epilepsy with febrile seizures plus, myoclonic astatic epilepsy and SMEI itself. We describe the five gene loci localized in children with febrile seizures (FEB 1 5), the three genes identified in patients with generalized epilepsy with febrile seizures plus (GEFS+ 1 3) and the de novo mutations of gene SCN1A that have been identified to date in children with SMEI.
Conclusions: SMEI, the severest form of the phenotypic spectrum of febrile seizures plus, is a channelopathy that is produced de novo, that is, during meiosis. Its prognosis may be conditioned by the kinds of mutations it is due to, and which are very different to those that induce other, more benign epileptic syndromes from the same phenotypic spectrum.