Oculopharyngeal muscular dystrophy
- Muscular dystrophy, oculopharyngeal
Your QuestionMy husband has a family history of oculopharyngeal muscular dystrophy. I am worried that he may be affected. Can the symptoms of this condition occur at earlier ages in susequent generations? Could this condition affect sperm mobility? What are the chances that a child we have together could be affected?
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Questions on this page
- What is oculopharyngeal muscular dystrophy?
- What are the symptoms of oculopharyngeal muscular dystrophy?
- What causes oculopharyngeal muscular dystrophy?
- How is oculopharyngeal muscular dystrophy inherited?
- Can the symptoms of oculopharyngeal muscular dystrophy occur at earlier ages in susequent generations (a phenomenon known as anticipation)?
- Could being affected by oculopharyngeal muscular dystrophy affect sperm mobility?
- What are the risks posed to any child that my husband and I would have to be affected by oculopharyngeal muscular dystrophy?
Individuals with oculopharyngeal muscular dystrophy may also have double vision (diplopia) and frequently have weakness in the muscles near the center of the body (proximal muscles), particularly muscles in the upper legs and hips. The weakness progresses slowly over time, and people may need the aid of a cane or a walker. Rarely, affected individuals need wheelchair assistance. Life expectancy on this condition is not reduced.
Oculopharyngeal muscular dystrophy (OPMD) is caused by mutations in the PABPN1 gene. The PABPN1 gene provides instructions for making a protein that is active (expressed) throughout the body. In cells, the PABPN1 protein plays an important role in processing molecules called messenger RNAs (mRNAs), which serve as genetic blueprints for making proteins. The protein acts to protect the mRNA from being broken down and allows it to move within the cell.
Mutations in the PABPN1 gene that cause OPMD result in a PABPN1 protein that forms clumps within muscle cells, and hence they cannot be broken down. These clumps are thought to impair the normal function of muscle cells and eventually cause cells to die. The progressive loss of muscle cells most likely causes the muscle weakness seen in people with OPMD. It is not known why abnormal PABPN1 proteins seem to affect muscle cells in only certain parts of the body.
Most cases of oculopharyngeal muscular dystrophy (OPMD) are inherited in an autosomal dominant manner, which means one copy of the altered (mutated) gene in each cell is sufficient to cause the condition. Individuals have two copies of each gene; one copy having been inherited from each parent. An individual with the autosomal dominant form of OPMD may have inherited the condition from an affected parent, or less commonly, the condition may occur for the first time in the affected individual. Each child of an affected individual with this form of OPMD has a 50% (1 in 2) chance to be affected and a 50% chance to be unaffected.
Less commonly, OPMD is inherited in an autosomal recessive manner, which means that both copies of the disease-causing gene in each cell must have a mutation for an individual to be affected. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene (and are referred to as carriers), but they typically do not show signs and symptoms of the condition. When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) chance to be affected, a 50% (1 in 2) chance to be a carrier like each of the parents, and a 25% chance to be unaffected and not be a carrier. The children of an individual with autosomal recessive OPMD will always be carriers (obligate heterozygotes) for the disease-causing mutation. The risk of a child being affected if his/her parent has autosomal recessive OPMD is less than 1%.
Genetic counseling may help you both better understand the above-mentioned testing, your husband's health status, and the risk of passing this disease on to the next generation. Visit the Services section of the resources page to find a list of online resources that can assist you in finding a genetics clinic near you.
- McLoon L, Lee M. Muscular Dystrophy, Oculopharyngeal. National Organization for Rare Disorders (NORD). 2007; http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Muscular%20Dystrophy%2C%20Oculopharyngeal. Accessed 12/7/2008.
- Oculopharyngeal muscular dystrophy. Genetics Home Reference (GHR). December 2008; http://ghr.nlm.nih.gov/condition=oculopharyngealmusculardystrophy. Accessed 12/8/2008.
- Facts About Rare Muscular Dystrophies. Muscular Dystrophy Association (MDA). June 2008; http://www.mda.org/publications/fa-rareMD.html. Accessed 12/7/2008.
- Brais B, Rouleau GA. Oculopharyngeal Muscular Dystrophy. GeneReviews. June 2006; http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=opmd. Accessed 12/7/2008.
- Bernard Brais, M Phil, and Guy A Rouleau. Oculopharyngeal Muscular Dystrophy. GeneReviews. June 22, 2006; http://www.ncbi.nlm.nih.gov/books/NBK1126/. Accessed 5/2/2012.