Intermediate Phenotypes of ATP1A3 Mutations: Phenotype–Genotype Correlations

Abstract

BACKGROUND ATP1A3-related disorders include rapid-onset dystonia-parkinsonism (RDP or DYT12), alternating hemiplegia of childhood (AHC), and CAPOS syndrome (Cerebellar ataxia, Areflexia, Pes cavus, Optic atrophy, and Sensorineural hearing loss). CASE REPORT We report two cases with intermediate forms between RDP and AHC. Patient 1 initially presented with the AHC phenotype, but the RDP phenotype emerged at age 14 years. The second patient presented with levodopa-responsive paroxysmal oculogyria, a finding never before reported in ATP1A3-related disorders. Genetic testing confirmed heterozygous changes in the ATP1A3 gene in both patients, one of them novel. DISCUSSION Intermediate phenotypes of RDP and AHC support the concept that these two disorders are part of a spectrum. We add our cases to the phenotype-genotype correlations of ATP1A3-related disorders.