Appropriate first-tier genetic test for diagnostic testing or carrier screening for DMD or BMD; does not detect sequence variants. Recommended test for a known familial DMD large deletion or duplication previously identified in a family member; a copy of the family member’s test result documenting the known familial variant is required.
Multiplex Ligation-dependent Probe Amplification
Within 14 days
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 2 mL)
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Background information for Duchenne/Becker Muscular Dystrophy (DMD) Deletion/Duplication:
Characteristics: Symptoms of Duchenne muscular dystrophy (DMD) usually begin before age 6 and include fatigue, learning difficulties, muscle weakness (beginning in legs and pelvis), progressive difficulty walking with wheelchair needed at approximately 12 years and breathing difficulties and heart disease by age 20 years. Symptoms of Becker muscular dystrophy (BMD) are similar to DMD but start later and progress at a slower rate. Dilated cardiomyopathy has been observed in nearly all affected males and many female carriers of DMD and BMD.
Incidence: DMD: 1 in 3,500 male births, BMD: 1 in 19,000 male births.
Inheritance: X-linked; de novo mutations occur in one-third of cases.
Penetrance: Males: 100 percent. Females: Varies with X-chromosome inactivation.
Cause: Pathogenic DMD mutations.
Clinical Sensitivity: DMD: 55-75 percent, BMD: 75-90 percent.
Methodology: Multiplex ligation-dependent probe amplification (MLPA) to detect large exonic deletions/duplications.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: DMD base pair substitutions, small deletions/duplications, deep intronic, and regulatory region mutations will not be detected. Breakpoints for large deletions/duplications will not be determined. Diagnostic errors can occur due to rare sequence variation.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2011236||Duchenne/Becker MD (DMD) DelDup Specimen|
|2011237||Duchenne/Becker MD (DMD) DelDup Interp||21247-2|