Early-onset encephalopathy with paroxysmal movement disorders and epileptic seizures without hemiplegic attacks: About three children with novel ATP1A3 mutations.

OBJECTIVE: Heterozygous mutations in the ATP1A3 gene are responsible for various neurological disorders, ranging from early-onset alternating hemiplegia of childhood to adult-onset dystonia-parkinsonism. Next generation sequencing allowed the description of other phenotypes, including early-onset epileptic encephalopathy in two patients. We report on three more patients carrying ATP1A3 mutations with a close phenotype and discuss the relationship of this phenotype to alternating hemiplegia of childhood. METHODS: The patients' DNA underwent next generation sequencing. A retrospective analysis of clinical case records is reported. RESULTS: Each of the three patients had an unreported heterozygous de novo sequence variant in ATP1A3. These patients shared a similar phenotype characterized by early-onset attacks of movement disorders, some of which proved to be epileptic, and severe developmental delay. (Hemi)plegic attacks had not been considered before genetic testing. SIGNIFICANCE: Together with the two previously reported cases, our patients confirm that ATP1A3 mutations are associated with a phenotype combining features of early-onset encephalopathy, epilepsy and dystonic fits, as in the most severe forms of alternating hemiplegia of childhood, but in which (hemi)plegic attacks are absent or only suspected retrospectively.