At the molecular level, DM1 caused by an expansion of CTG trinucleotide repeats within the 3′ untranslated region of the dystrophia myotonica protein kinase (DMPK) gene on chromosome 19, where disease severity demonstrates a direct correlation with the number of repeats (Hunter et al., 1992; Harley et al., 1993; Redman et al., 1993; Morales et al., 2012). The gene discussed is DMPK; the disease is myotonic dystrophy type 1.