ATP1A3 gene has been involved in five clinical neurological entities [8]: (1) RDP; (2) alternating hemiplegia of childhood (AHC); (3) CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss) syndrome; (4) early infantile epileptic encephalopathy; and (5) Relapsing encephalopathy with cerebellar ataxia (RECA). This evidence concerns the gene ATP1A3 and early-infantile DEE.