Inheritance is typically autosomal dominant with incomplete penetrance, although other inheritance patterns are recognized (see PCDH19 for example). Complex inheritance is also seen.
A number of genes have been linked to this epilepsy syndrome including: SCN1A (identified in 10% of GEFS+ families), SCN1B, and others.
A family history is required for diagnosis of this syndrome. Individuals in a family may have febrile seizures, febrile seizures plus, an idiopathic generalized epilepsy syndrome or an epilepsy syndrome with encephalopathy e.g. epilepsy with myoclonic atonic seizures or Dravet syndrome.