This is a very heterogeneous form of epilepsy, inherited in an autosomal dominant fashion, with age-specific manifestations and variable penetrance (about 60% in the original families). Febrile seizures are the most common feature, and seizures precipitated by fever tend to occur throughout childhood. Afebrile seizures of varying types, generalised tonic-clonic, myoclonic, atypical absence, and less commonly focal seizures, develop later in childhood. Status epilepticus can occur. The severity during the active phase is very variable, but the condition often remits by late childhood or early adult life. The phenotype is so broad that it is arguable whether this condition really deserves the epithet 'syndrome'. Certainly, however, the families inherit epilepsy, and many different mutations in either the a or P subunits of the voltage-gated sodium channel genes SCNIA and SCNIB, and more recently the y2 subunit of the GABA-A receptor GABRG2 gene have been identified, in families from many geographical locations. Functional studies have confirmed that these mutations confer abnormal membrane excitability. A really interesting question is how often sporadic mutations of sodium channel GABA receptor genes underlie sporadic febrile convulsions or even cryptogenic epilepsy, and this is a subject of active research. Another intriguing aspect of GEFS+ is its marked phenotypic variability, both within and across families. Digenic or oligogenic inheritance has been postulated to explain some of this variability. The seizures are treated along conventional lines for secondarily generalized epilepsy, and the prognosis is variable, with spontaneous remission of seizures in some cases and intractable epilepsy in others.
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