ATP1A3 and Rare pervasive developmental disorder: More recently other phenotypes have been associated with variants in ATP1A3, such as cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensory motor hearing loss (CAPOS syndrome),5 relapsing encephalopathy with cerebellar ataxia6/fever‐induced paroxysmal weakness encephalopathy,7 early‐onset epileptic encephalopathy,8 rapid‐onset ataxia in childhood9 or adulthood,10 childhood‐onset schizophrenia,11 and autism spectrum disorders.12