Mutations in the human voltage-gated K<sup>+</sup> channel subunit K<sub>V</sub> 4.3-encoding KCND3 gene have been associated with the autosomal dominant neurodegenerative disorder spinocerebellar ataxia types 19 and 22 (SCA19/22).
Spinocerebellar ataxia type 19 (SCA19), allelic with spinocerebellar ataxia type 22 (SCA22), is a rare syndrome caused by mutations in the KCND3 gene which encodes the potassium channel Kv4.3.
We identified a de novo KCND3 mutation causing the most marked change in Kv4.3's channel properties reported so far, which correlated with a severe and unique spinocerebellar ataxia (SCA) type 19/22 disease phenotype.
Before the SCA19 locus was identified, the SCA22 symbol had been assigned to a locus on 1p21-q23 following a linkage study of a Chinese family with spinocerebellar ataxia.