DMPK and myotonic dystrophy type 1: Myotonic Dystrophies type 1 and type 2 are complex genetic diseases caused by unstable CTG expansions (from 37 to up to several thousand repeats) in the 3′UTR of the DMPK gene (DM1) and CCTG expansions in the first intron of the CNBP (also known as ZNF9) gene (DM2) [1,2].