Mutations of the ARX gene are the most frequent mutations of X-linked ID (XLID), and they are responsible for a wide phenotypic spectrum including S-XLID and NS-XLID forms [12–15], as well as X-linked lissencephaly with abnormal genitalia (XLAG), hydranencephaly with abnormal genitalia (HYD-AG), X-linked infantile spasm (ISSX), X-linked myoclonic seizures, spasticity and ID (XMESID), Partington syndrome (PRTS), Ohtahara syndrome, Proud syndrome, and idiopathic infantile epileptic dyskinesia encephalopathy (IEDE) [8, 16–20]. The gene discussed is ARX; the disease is cask-related x-linked intellectual disability.