DM is an autosomal dominant disorder whose multisystemic features originate form nucleotide expansions: (CTG)n in the dystrophy myotonic protein kinase (DMPK) gene on chromosome 19q13 in DM type 1 (DM1), or (CCTG)n in intron 1 of the CNBP gene (previously known as zinc finger 9 gene, ZNF9) on chromosome 3q21 in DM type 2 (DM2). The gene discussed is DMPK; the disease is myotonic dystrophy type 2.