DM2 (OMIM: 602668), initially named proximal myotonic myopathy due to the greater weakness of proximal compared to distal muscles2, is caused by a tetranucleotide (CCTG) expansion in intron 1 of the CCHC-type zinc finger nucleic acid binding protein gene (CNBP, also known as ZNF9)3. Here, CNBP is linked to Proximal myotonic myopathy.