Molecular and clinical characteristics of myotonic dystrophy type 1 in koreans.
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.
Kim
So Yeon
SY
Department of Laboratory Medicine, Seoul National University College of Medicine and Seoul National University Hospital, Korea.
Kim
Ji Yeon
JY
Kim
Gyoung Pyoung
GP
Sung
Jung-Jun
JJ
Lim
Kyu Sang
KS
Lee
Kwang-Woo
KW
Chae
Jong Hee
JH
Hong
Yoon-Ho
YH
Seong
Moon-Woo
MW
Park
Sung Sup
SS
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
C585517:DMPK protein, human; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases