DM1 is caused by expansion of a (CTG)(n) repeat in the DMPK gene, while DM2 is caused by expansion of a (CCTG)(n) part of a complex repetitive motif (TG)(n)(TCTG)(n)(CCTG)(n) in the ZNF9 gene [26]. This evidence concerns the gene DMPK and myotonic dystrophy type 1.