What causes Duchenne muscular dystrophy?

In Duchenne muscular dystrophy (DMD), the fibres that make up the muscles gradually waste away. In 1986, scientists found that the muscle cells of boys with DMD are missing a vital protein, called dystrophin. Scientists think that dystrophin may help to hold the cells together in healthy muscles. In boys with DMD the gene that makes dystrophin is either altered or partly missing.

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Dystrophin is stained brown in normal muscle (left), but is absent in muscle from a boy with DMD (right).

How is Duchenne muscular dystrophy inherited?

Duchenne muscular dystrophy (DMD) is caused by an altered gene found on the X-chromosome, so the condition usually affects only boys. In some cases, the disorder appears 'out of the blue', following a new mutation in the unfertilised egg. In others, DMD is inherited from a carrier mother, who is usually unaffected herself. A carrier mother has a one-in-four chance of having an affected son and a one-in-four chance of having a carrier daughter.

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Inheritance of Duchenne muscular dystrophy.

Is there a test for Duchenne muscular dystrophy?

Duchenne muscular dystrophy (DMD) is a quite rare genetic condition, so people are not routinely tested to see if they carry it. But when a boy is diagnosed with DMD, his family may seek genetic counselling to find out whether other relatives carry the altered gene. Doctors can work out who is at risk by studying the family tree. A genetic test can usually establish which female relatives are DMD carriers.

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Human chromosomes highlighted by fluorescent probes which bind to specific sequences of DNA, showing deletion in the DMD gene (red).

 

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Wellcome trust

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