Myotonic Dystrophy type 1 (DM1, OMIM# 160900) is caused by an expanded CTG tract in the 3′ untranslated region (3′ UTR) of the dystrophia myotonica protein kinase (DMPK) gene that mainly affects muscular and neuronal lineages (Brook et al., 1992; Mahadevan et al., 1992; Udd and Krahe, 2012). The gene discussed is DMPK; the disease is myotonic dystrophy type 1.