Duchenne and Becker Muscular Dystrophies
Gene: DMD
Protein: dystrophin
Clinical Characteristics
Duchenne Muscular Dystrophy (DMD)
- Affects males
- Progressive symmetrical muscular weakness, proximal greater than distal
- Calf pseudohypertrophy
- Onset before age 5
- Wheelchair dependency before age 13
- Serum creatine phosphokinase (CK) concentration greater than 10 times normal
Becker Muscular Dystrophy (BMD)
- Affects males
- Later onset of symptoms
- Wheelchair dependency after age 16; some remain ambulatory
- Serum CK concentration greater than 5 times normal
DMD-Associated Dilated Cardiomyopathy
- Affects males and females
- Dilated cardiomyopathy (DCM) with congestive heart failure
- Males with onset between ages 20 to 40 with rapid progression
- Females with onset later in life with slower progression
- Usually no clinical evidence of skeletal muscle disease
Inheritance pattern: X-linked; carrier females may be affected with dilated cardiomyopathy
What Can Be Learned From This Test
Testing is performed by multiplex PCR of select exons of the DMD gene. Of the 79 exons in the DMD gene, 47 are amplified. These 47 exons are located throughout the gene and concentrated in regions that are known to be frequently deleted.
Deletions that include one or more of these exons will be detected by this assay. Deletions account for 65% of the mutations in DMD and 85% of the mutations in BMD. This test will not detect large duplications, small deletions or insertions, point mutations or splicing mutations. Our lab does not perform sequencing of the DMD gene.
A negative test result does not rule out a diagnosis of Duchenne or Becker muscular dystrophy, since 15-35% of mutations are nondeletion mutations. There are no other genes known to be associated with Duchenne and Becker muscular dystrophies.
A negative test does not rule out a genetic cause of muscular dystrophy. There are many other genes associated with different types of muscular dystrophy.
Our lab does not perform carrier testing in females for mutations in the DMD gene.
Sample Requirements
Draw 2ml–4ml of blood in EDTA/purple-top tube (minimum of 1ml–2ml for infants).
Turnaround time: 10-14 business days
CPT Codes and Cost
Select Exon Deletion Testing
- Code: 81161
- Cost: $525