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Test Code: DBMLPA
Description: Duchenne and Becker muscular dystrophies (DMD and BMD) are X- linked disorders caused by mutations in the DMD gene, which lead to abnormalities in the large cytoskeletal protein dystrophin. The DMD gene contains ≥79 exons spread over 2500 kb at Xp21. Due in part to its large size, at least 65% of DMD gene mutations are deletions and at least 5% are duplications of one or more exons.

The dystrophinopathies are characterized by a spectrum of muscle disease that ranges from mild to severe. Duchenne muscular dystrophy usually presents in early childhood with delayed milestones, including delays in sitting and standing independently. Proximal weakness causes a waddling gait and difficulty climbing. DMD is rapidly progressive, and affected children become wheelchair-bound by the age of 12 years. Cardiomyopathy occurs in all patients after age 18. Few survive beyond the third decade, and respiratory complications and cardiomyopathy are the common causes of death. The incidence of DMD is approximately one in 3500 male births. Becker muscular dystrophy is characterized by later-onset skeletal muscle weakness; patients remain ambulatory into their twenties. Despite the milder skeletal muscle involvement, heart failure from dilated cardiomyopathy (DCM) is a common cause of morbidity and the most common cause of death. Mean age of death is in the mid-forties. In this group of patients, approximately 85% of mutations are deletions. The incidence is ~1 in 30,000 males. X-linked dilated cardiomyopathy is characterized by left ventricular dilation and congestive heart failure. Carrier females are at increased risk for dilated cardiomyopathy.

This assay is not appropriate for prenatal testing.


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