Duchenne dystrophy and Becker dystrophy are the second most prevalent muscular dystrophy. They are caused by mutations of the dystrophin gene at the Xp21.2 locus. The DMD gene provides instructions for making a protein called dystrophin. These forms of muscular dystrophy occur almost exclusively in males. DMD/BMD together affect 1 in 3,500 newborn males worldwide. Females who carry a DMD gene mutation may have muscle weakness and cramping. These symptoms are typically milder than the severe muscle weakness and atrophy seen in affected males.
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DMD: This disorder manifests typically between 2 and 3 years of age, with affected children being wheelchair dependent by age 13 years. Cardiomyopathy occurs in almost all individuals with DMD after age 18 years. Few survive beyond the third decade, with respiratory complications and progressive cardiomyopathy being common causes of death into their 20s and 30s.
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BMD: Becker dystrophy typically becomes symptomatic much later and is milder. Ambulation is usually preserved until at least age 16, and many children remain ambulatory into adulthood. Most affected children survive into their 40s and 50s.

DMD/BMD is inherited in an X-linked recessive pattern. About 70% of DMD/BMD is caused by a single- or multi-exon deletion or duplication and ∼30% of single point mutations. In males (who have only one X chromosome), one altered copy of the gene is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. A female with one mutated copy of the gene is called a carrier. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females.

Uses multiplex PCR and Capillary Electrophoresis to determine the copy numbers of the 79 exons of DMD gene. The detection from DNA can be accomplished within 3 hours to determinate the exon deletions or duplications of DMD gene as a cause for Duchenne muscular dystrophy and/or Becker muscular dystrophy and for carrier screening.