Oculopharyngeal muscular dystrophy is a rare disease, presenting with bilateral ptosis and dysphagia, followed by slow progressive muscle weakness. The pathological hallmark of the disease is the presence of intranuclear inclusions in muscle cells. Inheritance is autosomal dominant in almost all cases. The mutation responsible is a short guanine-cytosine-guanine (GCG) expansion in the 'poly adenylate binding nuclear I protein' (PABN1) gene. This expansion is stable in subsequent generations and is translated into a polyalanine tract. The aberrant protein is found within the intranuclear inclusions and interferes with normal mRNA function.