Two genetic types of DM have been described corresponding to an expansion of, respectively, cytosine thymidine guanine (CTG) and CCTG repeats in non-coding regions (3′-untranslated region) of the myotonic dystrophy protein kinase (DMPK) gene for DM1, and zinc finger protein 9 (ZnF9) gene for DM2. This evidence concerns the gene DMPK and myotonic dystrophy type 2.