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Basic Facts about Becker Muscular Dystrophy

written by: •edited by: Paul Arnold•updated: 2/25/2010

Becker muscular dystrophy (BMD) is an X-linked recessive disease. In common with some other (but not all) muscular dystrophies it is an inherited genetic mutation of the dystrophin gene, which lies on the X chromosome.

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    One of the Types of Muscular Dystrophy

    Becker muscular dystrophy is a genetic disorder affecting males which causes muscle weakness and wasting. Its progression is slow and the typical age of diagnosis is 12, though the range can be wide, with the disease being diagnosed earlier in childhood or even well into adult life. The genetic disorder is not as severe as Duchenne muscular dystrophy. It involves a progressive weakness of the legs and pelvis and also the arms, neck and upper areas of the body. Symptoms are usually mild at first; a person may experience cramps or tend to be clumsy. Children with Becker are generally not very athletic. In adulthood walking may become more difficult, and on average most men with Becker will need a wheelchair for mobility when they’re in their late forties or earlier. Problems with facial muscles and swallowing are usually not present in BMD. Heart disease known as cardiomyopathy is sometimes a symptom.

    To find out whether an individual has BMD a blood test (to look for elevated levels of an enzyme called creatine kinase) and a muscle biopsy are needed.

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    Basic Facts about the Cause of Becker Muscular Dystrophy

    The cause of Becker muscular dystrophy is a mutation on the dystrophin gene. Dystrophin codes for the dystrophin protein which is located in muscle fibres. In BMD the protein is functional, but abnormally shaped and there’s usually not enough of it to go round. Or it can be of poor quality. As a consequence the muscle fibres break down and the muscles themselves become weaker over time. Having some dystrophin means that the severity and progression of the disease is not as great as in Duchenne muscular dystrophy, where the dystrophin protein is absent.

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    Basic Facts about the Genetics of Becker Muscular Dystrophy

    BMD is an X-linked recessive disease. Women have two X chromosomes, and so if there is a defective gene on one chromosome they will not contract Becker’s because of the correct version on their other sex chromosome. This will compensate for the genetic mutation. However, carrier women can sometimes experience mild symptoms of the disease. As men have one X and one Y chromosome they will develop symptoms if they inherit the defective gene.

    As BMD is an X-linked recessive disease the chances of a carrier woman passing on the defect is 50% in each pregnancy. Affected sons will develop the disease and affected daughters will be carriers. A man with the genetic defect will not pass it on to his sons, but all of his daughters will be carriers.

    Sometimes the mutation may even occur spontaneously in the creation of sperm or egg cells. The child would then be the first person in the family to have the mutated dystrophin gene.

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    No Cure for Genetic Disorder

    Currently there is no cure, gene therapy or otherwise, for BMD. Scientists are looking at ways of inducing the dystrophin gene to produce normal dystrophin protein. In theory, any treatment that is found to work for sufferers of Duchenne muscular dystrophy would be applicable to Becker.

    To keep the symptoms at bay for as long as possible, individuals are encouraged to exercise regularly and keep fit, as this is known to strengthen muscle fibres.