Here, we report two sisters from a non-consanguineous family, presenting generalized epilepsy with febrile seizures plus (GEFS+; MIM#613863) associated with an heterozygous mutation in the SCN9A gene, p.(Lys655Arg), inherited from the father that was asymptomatic for the crisis, and a novel de novo loss of function mutation in the exon 10 of the ANKRD11 gene, p.(Tyr1715*) in one sister with a clinical phenotype compatible with KBG syndrome (MIM#148050). Here, SCN9A is linked to idiopathic generalized epilepsy.