Genetics of generalized epilepsy

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Epilepsy is the name of a group of disorders where seizures occur. 5% of people will have at least one seizure. Seizures accompanied by fever (febrile) are common in early childhood. Most forms of epilepsy and febrile seizures have an inherited component. Progress in finding genes for common forms of epilepsy has been slow, probably because they are due to the interaction of a number of genes. Four genes for rare epilepsies with single gene inheritance have been identified. These genes code for subunits of ion channels in cells. We study families where many individuals have seizures and carefully diagnose the seizures types. This work has resulted in the description of 5 new inherited epilepsies and led to discovery of 3 of the 4 known genes. The most important new inherited epilepsy is Generalized Epilepsy with Febrile Seizures Plus (GEFS+). GEFS+ accounts for many children with febrile seizures restricted to early childhood, or where seizures continue into mid-childhood. GEFS+ families may contain an individual with severe generalized epilepsy with intellectual disability. In a Tasmanian family with GEFS+, we found a gene defect in the sodium channel of nerve cells in the brain. We plan to study more families with GEFS+. We believe that specific severe childhood epilepsies may occur in families with GEFS+. If so, then the underlying cause of these serious disorders may be gene defects of GEFS+. Finding such genes will help to understand the basis of seizures and ultimately lead to targeted therapies. The second major focus of our work on GEFS+ is to use family studies to understand how different types of seizures are inherited, and to gain insights into the gene interactions underlying common epilepsies. We plan to study isolated cases of GEFS+ for the gene defects found in families. This strategy will reveal whether the same genes are important in the genetics of the common epilepsies.