Genotype-phenotype relationship in a cohort of 131 Chinese patients with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant dynamic mutation disorder characterized by myotonia and muscle weakness. The genotype-phenotype relationship has not been clearly defined in Chinese patients.

The clinical and genetic characteristics of 131 patients from 105 pedigrees were retrospectively analyzed. Triplet-primed Polymerase Chain Reaction (PCR) and Flanking PCR were performed to analyze the CTG repeats in DMPK gene.

Among 131 DM1 patients, 64.9% were male, indicating a higher male admission rate, possibly due to limited diagnostic awareness in China. Notably, 11.5% of patients were not initially diagnosed in Neurology Department. The linear negative correlation between CTG repeat number and age of onset was no longer valid when CTG repeats exceeded approximately 400. Forced vital capacity (FVC) was negatively correlated with CTG repeat number, while no significant correlations were found with the Modified Scheltens score, creatine kinase, troponin T, lipid profile, glycosylated hemoglobin, fasting glucose, or BMI. In 16 families studied, CTG repeats expanded in 13 and contracted in 2. White matter lesions were detected in 97.9% of patients, predominantly in the supratentorial region, bilaterally affecting the frontal lobes, temporal poles, and deep white matter.

Our results provide insightful information on the clinical and genetic characteristics of the largest Chinese cohort of DM1 patients to date and clarify genotype-phenotype relationship.