At the molecular level, DM involves an aberrant CTG trinucleotide expansion in the DMPK gene (which induces myotonic dystrophy type 1, DM1)[15–17] or a CCTG tetranucleotide expansion in the intron 1 of the CNBP gene (myotonic dystrophy type 2, DM2)[18–20]. The gene discussed is DMPK; the disease is myotonic dystrophy type 2.