title: Frequency analysis and clinical characterization of spinocerebellar ataxia types 1, 2, 3, 6, and 7 in Korean patients.
abstract: BACKGROUND
  By genetic analysis, the CAG repeat expansion has been established in spinocerebellar ataxia (SCA) types 1, 2, 3, 6, and 7. Despite the genetic differentiation of SCA, the characterization of the phenotypes of various SCAs has been challenging for better clinical diagnosis.
  
  
  OBJECTIVE
  To analyze the frequencies and the clinical manifestations of SCA1, SCA2, SCA3, SCA6, and SCA7 in Korean patients.
  
  
  METHODS
  We performed genetic analysis in 253 unrelated Korean patients with progressive cerebellar ataxia. We compared the frequencies, inheritance patterns, and various clinical manifestations of patients with genetically confirmed SCA.
  
  
  RESULTS
  Among the 52 patients with expanded CAG repeat, the most frequent SCA type was SCA2, followed by SCA3, SCA6, SCA1, and SCA7. Nine patients (17%) had a negative family history of ataxia, mostly in SCA6. There were characteristic clinical features such as hypotonia and optic atrophy for SCA1; hyporeflexia for SCA2; nystagmus, bulging eye, and dystonia for SCA3; and macular degeneration for SCA7. Interestingly, 4 patients (1 with SCA2, 1 with SCA3, and 2 with SCA6) were misdiagnosed as having multiple-system atrophy because of the absence of family history and the presence of parkinsonism and urinary incontinence.
  
  
  CONCLUSIONS
  This study provides a detailed analysis of the clinical characteristics of the genetically defined CAG-repeat SCAs in Korean patients. Although phenotypes were heterogeneous, some clinical features may be helpful for clinical diagnosis. However, genetic studies for SCA are needed despite uncertain family history or the presence of atypical clinical features causing misdiagnosis as atypical parkinsonism.
authors.affiliation: Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. wylee@smc.samsung.co.kr
authors.forename: Won Yong
authors.initials: WY
authors.lastname: Lee
authors.forename: Dong Kyu
authors.initials: DK
authors.lastname: Jin
authors.forename: Myung Ryurl
authors.initials: MR
authors.lastname: Oh
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Lee
authors.forename: Seng Mi
authors.initials: SM
authors.lastname: Song
authors.forename: Eun Ah
authors.initials: EA
authors.lastname: Lee
authors.forename: Gyeong-Moon
authors.initials: GM
authors.lastname: Kim
authors.forename: Jin Sang
authors.initials: JS
authors.lastname: Chung
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Lee
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D005260:Female; D005787:Gene Frequency; D006801:Humans; D007723:Korea / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020754:Spinocerebellar Ataxias / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D018911:Trinucleotide Repeats