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]. The gene discussed is CNBP; the disease is myotonic dystrophy type 1.