A novel mutation in KCNA1 causes episodic ataxia without myokymia

Hum Mutat. 2004 Dec;24(6):536. doi: 10.1002/humu.9295.


We describe a unique family in which several individual are affected with episodes of ataxia that best fit the phenotype of episodic ataxia type 2 (EA2). All of the affected family members had episodes typically lasting for several hours, and none of them had muscle abnormalities including myokymia. Episodic ataxia type 1 (EA1) was not considered initially as a clinical diagnosis for the affected individuals in this family. However, by linkage mapping, sequencing and polymorphism analysis, all affecteds were found to have a novel mutation in KCNA1. Numerous missense mutations have been described previously in KCNA1 that cause EA1. The mutation c.1025G>T replaces a highly conserved serine with isoleucine at position 342 (p.Ser342Ile) in the highly conserved fifth transmembrane domain of the KCNA1. This mutation leads to a distinct clinical phenotype without myokymia broadening the scope of clinical characteristics of EA1 and highlighting the heterogeneity of phenotypic effects from distinct missense mutations.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Amino Acid Sequence
  • Ataxia / genetics*
  • Ataxia / physiopathology
  • Chromosome Mapping
  • Chromosomes, Human, Pair 19
  • Female
  • Genetic Linkage
  • Humans
  • Kv1.1 Potassium Channel
  • Male
  • Molecular Sequence Data
  • Mutation, Missense*
  • Myokymia
  • Pedigree
  • Potassium Channels, Voltage-Gated / genetics*
  • Sequence Analysis, DNA


  • KCNA1 protein, human
  • Potassium Channels, Voltage-Gated
  • Kv1.1 Potassium Channel