Oculopharyngeal muscular dystrophy among Bulgarian Jews: a new cluster?

BACKGROUND: Oculopharyngeal muscular dystrophy (OPMD) produced by the (GCG)13 expansion mutation in the PABPN1 gene is frequent among Uzbek Jews in Israel. OBJECTIVES: To describe the phenotypic and genotypic features in five Bulgarian Jewish patients, from different families, with autosomal dominant OPMD. METHODS: We performed clinical follow-up, electrodiagnostic tests and mutation detection. Blood samples were obtained after informed consent and DNA was extracted; measurement of GCG repeats in both PABPN1 alleles and sequencing of OPMD mutations were performed according to standard techniques. RESULTS: We identified five patients (four females), aged 58 to 71 years, with bilateral ptosis, dysphagia, dysphonia (n = 3) and myopathic motor units by electromyography. In all patients we noticed proximal weakness of the upper limbs with winging scapulae in three of them. All cases shared the (GCG)13-(GCG)10 PABPN1 genotype. CONCLUSIONS: OPMD among Bulgarian Jews is produced by a (GCG)13 expansion, identical to the mutation in Uzbek Jews and French Canadians. In addition to the classical neurological and neuro-ophthalmological features, early shoulder girdle weakness is common in Bulgarian Jewish patients; this is an unusual feature during the early stages of OPMD produced by the same mutation in other populations. We suggest that besides the disease-producing GCG expansion, additional ethnicity-related genetic factors may influence the OPMD phenotype. OPMD is a rare disease, and the identification of five affected families in the rather small Bulgarian Jewish community in Israel probably represents a new cluster; future haplotype studies may elucidate whether a founder effect occurred.