Oculopharyngeal muscular dystrophy (OPMD) is a muscular disease of very late onset, most often after the age of fifty, and which mainly results in slowly progressive damage to the muscles of the eyelids, face, pharynx and pelvic girdle. Inherited in an autosomal dominant mode, it is found on all continents with several clusters identified in Quebec and Israel. The clinical diagnosis is confirmed by a genetic test which in the vast majority of cases shows an expansion of GCA or GCG triplets in the PABPN1 gene located on chromosome 14.
In an article published in July 2021, Japanese clinicians report the observation of a 78-year-old female patient with all the clinical features of OPMD, whose routine genetic test was negative. In the absence of the expected trinucleotide repeat, it was decided to sequence the entire PABPN1 gene, which revealed a point mutation (c.35G> C). This unusual pathological sequence variation had previously been reported in three English patients, which suggested the existence of a founder effect in Europe. This same mutation is at the origin of the replacement of a glycine in alanine in position 12. From a functional point of view, this results in an elongation of polyalanine residues comparable to that observed in the forms of OPMD with classical genotype.