Survival and CTG repeat expansion in adults with myotonic dystrophy type 1.

ABSTRACT

INTRODUCTION: An association is observed between the severity of myotonic dystrophy type 1 (DM1) and the genetic abnormality of cytosine-thymine-guanine (CTG) repeat expansion. It is unknown whether an association exists between survival and CTG repeat expansion. METHODS: In an adult 406-patient DM1 cohort, the phenotype, including survival age, was evaluated in relation to CTG repeat expansion. RESULTS: At study entry, age was 42 ± 12 (range 18-78) years, with a CTG repeat length of 629 ± 386 (range 54-1965). An inverse correlation was observed between CTG repeat length and the age at onset and younger DM1 phenotype. Over a follow-up of 9.2 ± 3.1 years, 118 (29.1%) patients died, including 60 of neuromuscular respiratory failure, 41 of cardiac causes, and 17 of non-neuromuscular, non-cardiac causes. There was an inverse relationship between all-cause survival and CTG length (relative risk 5.4 per log repeat, 95% confidence interval 2.9-10.2, P < 0.001). CONCLUSION: The data demonstrate a genotype-mortality association in DM1.