Clinical Significance of CTG Repeat Expansion in Korean Myotonic Dystrophy Patients

J Korean Neurol Assoc > Volume 17(4); 1999 > Article

Journal of the Korean Neurological Association 1999;17(4): 548-553.

한국인 근긴장성 이양증에서 CTG 반복확장의 임상적 의의

최병옥, 선우일남 ·김승민 ·이진성*·이은경**·박기덕***·정근호****·문준식*****

연세대학교 의과대학 신경과학교실,소아과학교실*,임상연구센터**,이화여자대학교 의과대학 신경과학교실***국립의료원****,연세대학교 원주의과대학 신경과학교실*****

Clinical Significance of CTG Repeat Expansion in Korean Myotonic Dystrophy Patients

Byung-Ok Choi, M.D., Il-Nam Sunwoo, M.D., Seung-Min Kim, M.D., Jin-Sung Lee, M.D.*, Eun-Kyung Lee**, Kee-Duk Park, M.D.***, Keun-Ho Chung, M.D.****, Joon-Shik Moon, M.D.*****

Department of Neurology, Pediatrics, and Clinical Research Center*, College of Medicine Yonsei University Department of Neurology, Ewha Womans University***, National Medical Center****, Yonsei University Wonju College of Medicine *****

Abstract

Background : Myotonic dystrophy is the most common type of muscular dystrophy affecting adults, associated with the expansion of triplet repeat DNA sequences. A hallmark of the inherited disease with trinucleotide repeat DNA expansion is the clinical and genetic anticipation. The copy numbers of the CTG repeat are known to be related to the severity and the onset age of clinical symptoms. Methods : The copy numbers of the CTG repeats were determined using PCR amplification and Southern blotting. The clinical manisfestations of 34 patients from 14 families who had the CTG repeat expansion were evaluated based on the muscular disability rating scale and the electrophysiological study. Results : There was a significant positive correlation between the clinical scores and the size of the amplification of trinucleotide repeat, and a negative correlation with the age of onset. In 9 patients with copy numbers of CTG repeats between 61 and 100, 8 cases were asymptomatic and myotonic discharges were not seen in 71% of patients. Larger expanded bands, earlier onset, and worse symptoms were evident with each successive generation. Conclusions : Molecular genetic analysis with CTG repeat expansion might be useful in the detection and the genetic counseling of myotonic dystrophy patients. J Kor Neurol Ass 17(4):548~553, 1999 Key Words : Myotonic Dystrophy, Clinical Significance, CTG Repeat Expansion, Myotonic Discharge, Anticipation