Unusual Phenotypic Variability in Paroxysmal Dystonia Associated with Rare ATP1A3 Mutation: A Case Report and Review.

Paroxysmal dyskinesias, marked by sudden involuntary movements, poses diagnostic challenges because of its heterogeneous nature and overlap with other movement disorders. Genetic factors, especially variants in the ATP1A3 gene, have been linked to various neurologic conditions, including paroxysmal dystonia. We report a 5-year-old patient with a rare ATP1A3 gene variant (c.2309T>G, p.(Leu770Arg)), previously documented in only 1 other patient. Unlike the earlier report, the patient presented distinct clinical features, with a focus on dystonia rather than hemiplegia and no intellectual impairment. This phenotypic variability highlights the challenges in diagnosis and treatment. We discuss differential diagnoses, including Alternating Hemiplegia of Childhood, and emphasize the need for comprehensive genetic testing and multidisciplinary care. Our study advocates for further research to better understand the spectrum of ATP1A3-related disorders and enhance diagnostic accuracy and patient management in paroxysmal dystonia.