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Oculopharyngeal muscular dystrophy (OPMD) is a form of late-onset slowly progressive myopathy characterized by eyelid ptosis, dysphagia and, sometimes by other cranial and limb-muscle involvement. Most early cases were reported in the French Canadian population but the disease was subsequently found to be ubiquitous. The disorder presents in the fourth to the sixth decade with progressive often symmetrical ptosis resulting in a compensating contraction of the frontalis muscle and therefore a suggestive posture with retroflexion of the neck. Dysphagia is also an early symptom and can lead to nasal regurgitation and severe episodes of aspiration if overlooked. Limb-girdle muscle weakness, especially in the pelvic girdle, is often noted but varies widely among individuals without any correlation with the severity of ptosis or dysphagia. Creatine kinase (CK) levels are slightly elevated and electromyogram (EMG) studies suggest a mild myopathic process. The best clue to the diagnosis, after the clinical distribution of muscle weakness, is the presence of intranuclear inclusions in the muscle fibers. Rimmed vacuoles are often seen but are less specific. The disease is transmitted as an autosomal dominant trait. Genetic studies are now available and can establish the molecular signature of the disease. A short GCG-triplet repeat expansion (over 7 repeats) in the gene encoding the PABPN1 protein (on chromosome 14q) is pathognomonic of OPMD. However, the disease pathogenesis remains unclear. Supportive treatment is available and consists of eyelid surgery and myotomy of the cricopharyngeal muscle in carefully selected cases. |