ATP1A3 and Parkinson disease: Most common phenotypes: AHC, RDP, CAPOS, D-DEMØ. AHC starts in infancy and presents with episodes of hemiplegia and often hemidystonia. It usually evolves with epilepsy and loss of developmental milestones, and often persistent movement disorder. The RDP phenotype does not usually cause paroxysmal dystonia, but persistent dystonia and/or parkinsonism of subacute onset. Paroxysmal ataxia, later becoming persistent, is also described in ATP1A3 mutations. Epilepsy is most consistently associated with AHC and has infantile onset in most.