Genetic epilepsy with febrile seizures plus Refining the spectrum

Objective: Following our original description of generalized epilepsy with febrile seizures plus (GEFS1) in 1997, we analyze the phenotypic spectrum in 409 affected individuals in 60 families (31 new families) and expand the GEFS1 spectrum. Methods: We performed detailed electroclinical phenotyping on all available affected family members. Genetic analysis of known GEFS1 genes was carried out where possible. We compared our phenotypic and genetic data to those published in the literature over the last 19 years. Results: We identified new phenotypes within the GEFS1 spectrum: focal seizures without preceding febrile seizures (16/409 [4%]), classic genetic generalized epilepsies (22/409 [5%]), and afebrile generalized tonic-clonic seizures (9/409 [2%]). Febrile seizures remains the most frequent phenotype in GEFS1 (178/409 [44%]), followed by febrile seizures plus (111/409 [27%]). One third (50/163 [31%]) of GEFS1 families tested have a pathogenic variant in a known GEFS1 gene. Conclusion: As 37/409 (9%) affected individuals have focal epilepsies, we suggest that GEFS1 be renamed genetic epilepsy with febrile seizures plus rather than generalized epilepsy with febrile seizures plus. The phenotypic overlap between GEFS1 and the classic generalized epilepsies is considerably greater than first thought. The clinical and molecular data suggest that the 2 major groups of generalized epilepsies share genetic determinants.National Health and Medical Research Council of Australia [628952, 1091593, 466671, 1006110, 1104831, 1032603, 1063799]SCI(E)ARTICLE121210-12198