Based on the standards and guidelines set forth by the American College of Medical Genetics (ACMG) [28], we employed multiple criteria to assess the clinical significance of the heterozygous KCND3 c.1256G>A (p.R419H) variant identified in a patient with slowly progressive cerebellar ataxia, parkinsonism, cognitive dysfunction, and brain ion accumulation. Here, KCND3 is linked to Parkinsonism.