title: Molecular and clinical characteristics of myotonic dystrophy type 1 in koreans.
abstract: BACKGROUND
  Myotonic dystrophy type 1 (DM1) is an autosomal-dominant muscular dystrophy caused by expansion of cytosine-thymine-guanine (CTG) trinucleotide repeats in the myotonic dystrophy protein kinase (DMPK) gene. The clinical features of DM1 are multisystemic and highly variable, and the unstable nature of CTG expansion causes wide genotypic and phenotypic presentations. The aim of this study was to characterize the molecular and clinical spectra of DM1 in Koreans.
  
  
  METHODS
  The CTG repeats of 283 Korean individuals were tested by PCR fragment analysis and Southern blot. The following characteristics were assessed retrospectively: spectrum of CTG expansions, clinical findings, genotype-phenotype correlation, anticipation, and genetic instability.
  
  
  RESULTS
  One-hundred twenty-four patients were confirmed as DM1 by molecular tests, and the CTG expansions ranged from 50 to 2,770 repeats (median 480 repeats). The most frequent clinical features were myotonia, muscular weakness, and family history. Patients with muscular weakness or dysfunction of the central nervous system harbored larger CTG expansions than those without each symptom (P<0.05). The age of onset was inversely correlated with the size of the CTG expansion (gamma=-0.422, P<0.001). The instability of CTG expansion representing as the maximum difference between sibships was observed from 50 to 700 repeats in nine families. Clinical anticipation and the increase in CTG repeat were significantly higher in maternally transmitted alleles (P=0.002).
  
  
  CONCLUSIONS
  Molecular genetic tests are not only essential for diagnosis, but also helpful for suggesting the spectrum and relationship between genotype and phenotype in Korean DM1 patients.
authors.affiliation: Department of Laboratory Medicine, Seoul National University College of Medicine and Seoul National University Hospital, Korea.
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Kim
authors.forename: Ji Yeon
authors.initials: JY
authors.lastname: Kim
authors.forename: Gyoung Pyoung
authors.initials: GP
authors.lastname: Kim
authors.forename: Jung-Jun
authors.initials: JJ
authors.lastname: Sung
authors.forename: Kyu Sang
authors.initials: KS
authors.lastname: Lim
authors.forename: Kwang-Woo
authors.initials: KW
authors.lastname: Lee
authors.forename: Jong Hee
authors.initials: JH
authors.lastname: Chae
authors.forename: Yoon-Ho
authors.initials: YH
authors.lastname: Hong
authors.forename: Moon-Woo
authors.initials: MW
authors.lastname: Seong
authors.forename: Sung Sup
authors.initials: SS
authors.lastname: Park
mesh_terms: D015139:Blotting, Southern; D003627:Data Interpretation, Statistical; D005260:Female; D005838:Genotype; D006801:Humans; D007723:Korea; D008297:Male; D009223:Myotonic Dystrophy / Q000175:diagnosis* / Q000235:genetics*; D065636:Myotonin-Protein Kinase; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D012189:Retrospective Studies; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
chemical_list: C585517:DMPK protein, human; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases