Phenotypic overlap of alternating hemiplegia of childhood and CAPOS syndrome

Heterozygous mutations of the ATP1A3 gene cause rapid-onset dystonia-parkinsonism (RDP)1,2 and alternating hemiplegia of childhood (AHC).3,4 Intermediate AHC/RDP presentations and phenotypic diversity emerge.5 Aiming at identification of ATP1A3 -related conditions beyond classical RDP or AHC phenotypes, we loosened the criteria for mutation analysis of this gene in patients displaying features evocative of AHC or RDP. We describe a 12-year-old boy with an unreported clinical presentation associated with a novel missense mutation of the ATP1A3 gene.