Becker muscular dystrophy is caused by different variations in the same DMD gene that causes Duchenne.
“The terminology of the DMD gene can be confusing in the sense that a mutation in the DMD gene doesn’t necessarily cause Duchenne,” says Carolina Tesi Rocha, MD, a clinical professor of neuromuscular medicine with Stanford Medicine in Palo Alto, California.
Becker is less common than Duchenne, and also less disabling — the muscles have some dystrophin, although not enough for completely normal function.
While Becker has 60 to 70 percent of variations that are deletions, like Duchenne, 20 percent of its variations are duplications, and 5 to 10 percent are single nucleotide variants or other smaller changes.
The production of dystrophin is related to the type of deletion occurring in the gene. If the deletion is characterized as “in-frame,” the form of muscular dystrophy is more likely to be Becker. If the deletion is defined as “out-of-frame,” the type of MD is likely to be Duchenne.
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