Oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy
Classification and external resources
MuscularDystrophy
ICD-10	G71.0
ICD-9	359.1
OMIM	164300
DiseasesDB	29869
MeSH	D039141
GeneReviews	Oculopharyngeal Muscular Dystrophy

Oculopharyngeal muscular dystrophy (OPMD) can be autosomal dominant^[1] neuromuscular disease or autosomal recessive which appears in early middle age (fifth decade).^[2] The most common inheritance of OPMD is autosomal dominant, which means only one copy of the mutated gene needs to be present in each cell. Children of an affected parent have a 50% chance of inheriting the mutant gene. Generally, autosomal dominant inheritance have a strong family tie. Less commonly, OPMD can be inherited in a autosomal recessive pattern, which means that two copies of the mutated gene need to be present in each cell, both parents need to be carries of the mutated gene, and usually show no signs or symptoms. The PABPN1 mutation leads to a polyalanine tract that is 11 alanines long.^[3] 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.^[4][5]

Signs and symptoms

Progressive ptosis (drooping of eyelids) and weakness of the extraocular muscles is the initial clinical finding.. Dysphagia (difficulty swallowing) the swallowing difficulties begin with food but as the condition worsens liquids become difficult to swallow as well. Atrophy (weakness and wasting of the tongue). Problems taking in food can lead to malnutrition. proximal limb weakness develops later on in the disease, and usually occurs near the center of the body, particularly muscles in the upper legs and hips. This condition progresses slowly over time and individuals may need assistance of a cane or walker, but rarely will they need a wheelchair.^[2][3]

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.^[6]

Treatment

The condition does not generally reduce lifespan and there is no specific treatment, but there are many ways to Palliative medicinehelp manage symptoms. Extreme difficulty in swallowing may result in the insertion of a gastrointestinal feeding tube.^[4] Glasses can be fitted with fine metal bars that lift up the drooping eyelids. A consistent diet planned with the help of a dietitian along with exercises taught by a speech therapist can assist with mild symptoms of dysphagia. Some surgeries are available that can reduce ptosis and dysphagia. . Cutting one of the throat muscles internally, an operation called cricopharyngeal myotomy, can be one way to ease symptoms in more severe cases. An individual can also have a balloon inflated to dilate the gullet. With all surgical procedures, they come with many risk factors and the choice for treatment depends upon the individual and their needs.^[7][8]

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.^[9] The disease is uncommon in Asian populations.^[10]

References

External links

• opmd at NIH/UW GeneTests
• Muscular Dystrophy Association's website in Greece
• Oculopharyngeal muscular dystrophy at NIH's Office of Rare Diseases
• GeneReviews Washington State University, funded by NIH