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The dystrophinopathies are a spectrum of muscle diseases, with onset from childhood to adulthood and of varying severity. Duchenne muscular dystrophy (DMD) is the most frequent muscle disease in children. The birth prevalence of DMD is around 1 in 3500 live born males. The milder Becker muscular dystrophy (BMD) has a lower birth prevalence of around 1 in 18,500 live born males. DMD and BMD are X-linked recessive diseases caused by mutations in the dystrophin gene. More recently, DMD-associated cardiomyopathy (DCM) with congestive heart failure has been identified, which can occur in males age 20-40 on average and in female carriers later in life. Males with DCM typically do not have muscle weakness and are often diagnosed as ‘subclinical BMD’.
Deletions in the dystrophin gene make up approximately 65% of mutations in individuals with DMD and about 85% of mutations in BMD. Duplications make up 6-10% of mutations in individuals with DMD or BMD.
Using multiplex ligation-dependent probe amplification (MLPA), this test will detect >99% of deletions and duplications in the dystrophin gene, leading to an overall detection rate of about 70-75% for DMD and 90-95% for BMD. A negative test in patients with strong clinical suspicion of DMD or BMD should be followed by dystrophin gene sequencing
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