DMPK and myotonic dystrophy type 2: DM1 and DM2 are autosomal dominant disorders caused by microsatellite, or short tandem repeat (STR), CTG and CCTG expansions (exp) encoded in either the 3′ untranslated region (UTR) of DMPK (DM1) or the first intron of CNBP (DM2), respectively.