CTG repeat lengths of the DMPK gene in myotonic dystrophy patients compared to healthy controls in Thailand

Abstract

Myotonic dystrophy (DM) is frequently associated with large expansions of the cytosine-thymine-guanine (CTG) repeat in the myotonic dystrophy protein kinase gene (DMPK). The frequency of distribution of the CTG repeat length in normal alleles of several populations is well correlated with the prevalence of DM. Therefore, we studied the CTG repeat length of the DMPK gene in DM patients and controls in Thailand. Only seven typical patients with DM from six unrelated families were identified, all with large pathological CTG repeat expansions (> 400 repeats) in the DMPK gene. Only 2.75% of controls had normal CTG repeat alleles > 18 repeats. The frequency distribution of the CTG-repeat alleles in the normal Thai population is similar to that of the Taiwanese population (χ² with Yates correction = 1.393; p = 0.2379). These data suggest that the incidence of DM might be rare in Thailand, where the risk of developing DM is possibly similar to that in Taiwan.