DMPK and myotonic dystrophy type 1: Myotonic dystrophy type 1 (DM1) is an autosomal dominant degenerative neuromuscular disease [1–3] caused by a nucleotide triplet (CTG) repeat expansion within the 3′ untranslated region of the Dystrophy Myotonic Protein Kinase (DMPK) gene [4].