The short expansion of a GCG or GCA trinucleotide repeat (from GCN10 to GCN11–17) encoding a polyalanine tract at the N terminus of the polyadenylate (polyA) binding protein nuclear 1 gene (PABPN1, also known as PABP2) is a common cause of OPMD. This evidence concerns the gene PABPN1 and oculopharyngeal muscular dystrophy.