J Korean Neurol Assoc.  1999 Jul;17(4):548-553.

Clinical Significance of CTG Repeat Expansion in Korean Myotonic Dystrophy Patients

• Choi BO
• SunWoo IN
• Kim SM
• Lee JS
• Lee EK
• Park KD
• Jung KH
• Moon JS

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.

Keyword

Myotonic Dystrophy; Clinical Significance; CTG Repeat Expansion; Myotonic Discharge; Anticipation

MeSH Terms

Adult
Age of Onset
Anticipation, Genetic
Base Sequence
Blotting, Southern
DNA
Genetic Counseling
Humans
Molecular Biology
Muscular Dystrophies
Myotonic Dystrophy*
Polymerase Chain Reaction
Trinucleotide Repeats
DNA