Interestingly, a number of missense mutations across this C-terminal portion of the ARX gene including the Aristaless domain lead to Early Infantile Epileptic Encephalopathy (MIM#308350) or in one case the severe brain malformation phenotype of lissencephaly, X-linked 2 (MIM#300215). Here, ARX is linked to genetic developmental and epileptic encephalopathy.