DMPK and myotonic dystrophy type 1: There are two genetically distinct forms, Myotonic dystrophy type 1 (DM1, Steinert’s disease) caused by CTG repeat expansion in the 3′ UTR region of the myotonic dystrophy protein kinase (DMPK) gene, and Myotonic dystrophy type 2 (DM2, proximal myotonic myopathy) due to CCTG repeats in the intron 1 of the CNBP gene (also known as CCHC-type zinc finger, nucleic acid binding protein).