Oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant neuromuscular disease which appears in early middle age (fifth decade). OPMD is an example of a trinucleotide repeat disorder caused by expanding (GCN)10 to (GCN)11-17 at the 5' end of the coding region for PABPN1. This expands the polyalanine tract at the N-terminus of PABPN1 from 10 to 11-17 alanines.

Signs and symptoms
Progressive ptosis (drooping of eyelids) and weakness of the extraocular muscles is the initial clinical finding.. Dysphagia (difficulty swallowing) and proximal limb weakness develops later on in the disease.

Diagnosis
A muscle biopsy used to be the only method to diagnose the condition. Today a simple blood draw with genetic testing for the PABPN1 gene is more common. A distinction between OPMD and myasthenia gravis or mitochondrial myopathy must be made. The absence of family history and the fluctuation of symptoms in myasthenia gravis usually distinguish the two conditions.

Epidemiology
The disease is frequently seen in French Canadians, with a prevalence 1:1000. A 1997 study from Israel showed the second largest cluster of known individuals are of Bukhara Jews from Uzbekistan, with a calculated minimal prevalence of 1:600. The disease is uncommon in Asian populations.

Treatment
Treatment is supportive to the patient. The condition does not generally reduce lifespan. Extreme difficulty in swallowing may result in the insertion of a gastrointestinal feeding tube. Some surgeries are available that can reduce ptosis and dysphagia.