The condition is caused by unstable, simple nucleotide tandem repeats in thedystrophia myotonica protein kinase (DMPK) gene for myotonic dystrophy type 1(DM1) and in the cellular nucleic acid binding protein gene (CNBP) for myotonicdystrophy type 2 (DM2) [1, 2]. This evidence concerns the gene DMPK and myotonic dystrophy type 1.