Autosomal dominant with high penetrance.
Mutations in LGI1 are identified in 50% of families.
A family history of typical seizures with a dominant inheritance pattern with high penetrance is expected for the diagnosis of this syndrome. History should be carefully sought, as seizures comprise such mild symptoms that some individuals in families have not recognized their seizures. Sporadic cases do occur. Some families with LGI1 mutation have individuals with genetic/idiopathic generalized epilepsies, it is unknown whether this is by chance or linked to LGI1.