Myotonic dystrophy type 2 (DM2, OMIM 602688) results from an unstable tetranucleotide CCTG repeat expansion in intron 1 of the nucleic acid-binding protein (CNBP) gene (previously known as zinc finger 9 gene, ZNF9; OMIM 116955) on chromosome 3q21 (Liquori et al., 2001). The gene discussed is CNBP; the disease is Proximal myotonic myopathy.