Furthermore, we described a 37-year-old patient with a de novo KCND3 variant [c.901T>C (p.Ser301Pro)], previously reported in dbSNP as rs79821338, and a clinical phenotype paradigmatic of the early onset forms with neurodevelopmental disorder, epilepsy, parkinsonism-dystonia, and ataxia in adulthood, further expanding the clinical spectrum of this condition. The gene discussed is KCND3; the disease is epilepsy.