Myotonic dystrophy type 1 (DM1) is the one of the most common muscular dystrophies in adult patients and is caused by an unstable expansion of CTG repeats in the DMPK gene; clinical features of DM1 include myotonia, mainly distal muscle weakness, and multisystemic involvement, including respiratory function, the heart, and the CNS. This evidence concerns the gene DMPK and myotonic dystrophy type 1.