DMPK and myotonic dystrophy type 1: DM1 is caused by the expansion of unstable repetitions of cytosine-thymine-guanine trinucleotide (CTG) in the 3’ untranslated region (3’UTR) of the Myotonic Dystrophy Protein Kinase (DMPK) gene located at chromosome 19q13.3 [4,6,7].