ATP1A3-Associated Paroxysmal Dystonia.

Background: ATP1A3 mutations are associated with a diverse set of distinct neurological syndromes and intermediate phenotypes that may include extra-neural features. Overall, genotype-phenotype correlations are weak. There are no consensus treatments.

Case report: Video and clinical documentation is provided for a patient with a novel ATP1A3 mutation (GRCh38:19:41982028:C:A;NM_152296.5:c.1072G>T;p.Gly358Cys). This highly deleterious variant (Combined Annotation Dependent Depletion [CADD] score-28.8, Rare Exome Variant Ensemble Learner [REVEL] score -0.992) is not present in gnomAD v.4.1.0. Clinical manifestations include recurrent stereotypical episodes of paroxysmal dyskinesias that include jaw-opening dystonia superimposed on a baseline of developmental delay with static cognitive impairment, mild ataxia, and hypotonia. Paroxysmal episodes are triggered by emotional excitement, heat, cold, exercise, chocolate, and menses. The paroxysmal events typically last 5 min. Oxcarbazepine and clonazepam have reduced the frequency of paroxysmal episodes.

Discussion: ATP1A3 mutations are associated with protean manifestations that may include paroxysmal non-epileptic events such as ataxia, dystonia, and paresis. Accordingly, ATP1A3 mutation screening, most commonly as a multi-gene panel, and assessment of variant deleteriousness and population frequency should be completed in individuals with non-classical phenotypes. Benzodiazepines and drugs that target voltage gaited sodium channels (e.g., oxcarbazepine) may be effective therapeutic options.

Highlights: ATP1A3 mutations should be considered in patients with paroxysmal non-epileptic neurological events which may show clinical overlap with paroxysmal non-kinesigenic dyskinesias.