What is Duchenne/Becker Muscular Dystrophy?

Duchenne/Becker muscular dystrophy (Duchenne) is the most common muscular dystrophy in children. It is a progressive disorder that causes muscles to become weaker over time until it affects the whole body. Duchenne is not contagious. About one out of every 5,000 boys has Duchenne, and about 20,000 babies worldwide are born with it each year. Duchenne mostly affects boys and reaches across all races and cultures. Parent Project Muscular Dystrophy (PPMD) estimates that there are about 15,000 young men, as well as a few young women, living with Duchenne today in the United States. Although genetic disorders are usually passed down from a parent to a child, Duchenne muscular dystrophy can occur even if no one in your family has had it before.

While there is yet no cure for Duchenne, and many parents are told that there is no hope and little help, Parent Project Muscular Dystrophy exists to offer the support and resources parents may not find anywhere else. There is hope — with more than 40 companies currently working on treatments for Duchenne and more than 20 drugs in clinical trial, there are tremendous reasons to hope. Knowledge is power, and informed and timely care can help people living with Duchenne live longer and with a much greater quality of life than ever before.

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Why does my child have Duchenne?

Duchenne is a “gender-linked,” or “X-linked” disorder. You may have someone in your family who has or had Duchenne. As a genetic disorder, Duchenne is passed down from a parent to a child, so it could already be in your family’s genes. But Duchenne muscular dystrophy can also occur due to a new, or spontaneous, genetic change (mutation), even if no one in your family has had it before. In fact, one out of every three cases of Duchenne are caused by a spontaneous mutation of the Duchenne gene, with no family history.

What causes Duchenne?

Males are born with one X-chromosome (from mom) and one Y-chromosome (from dad). Because males only have one X chromosome, if the X-chromosome they receive has a gene mutation that causes Duchenne, the male will be born with Duchenne.

Females are born with two X-chromosomes (1 from mom and 1 from dad). If females have 1, X-chromosome that has a gene mutation for Duchenne, the body will generally choose to “activate” the other normal X chromosome. If this happens, the female will be a carrier of Duchenne, meaning that she can pass Duchenne on to her sons, and her daughters can also be carriers, but she herself will have few, if any, symptoms of Duchenne. If the female’s body, for whatever reason, chooses to activate the X chromosome with the mutation for Duchenne, the female will still be a Duchenne carrier, but will exhibit, or “manifest,” symptoms of Duchenne. She will then be a “manifesting carrier” of Duchenne.

What causes the symptoms of Duchenne?

Duchenne is caused by mutations in the gene that encodes for a muscle protein called dystrophin. Dystrophin is in every single muscle fiber in our bodies. Dystrophin acts as the glue that holds muscles together and the “shock absorber” that allows muscles to contract and relax without being damaged.

Without dystrophin, muscles are not able to function or repair themselves properly. As muscles are used for normal day-to-day activity, tiny tears are created in the muscle. Because there is no dystrophin, the muscles can’t repair themselves by making new muscle, so the damaged muscle is replaced by fat and scar tissue. As muscle is replaced, the person with Duchenne loses muscle function and strength. There are many muscles in the body (skeletal muscles, heart muscles, breathing muscles, etc.). Because there are so many muscles in the body, many parts of the body can be affected by Duchenne. For that reason, people living with Duchenne need care for many areas of the body.

Becker muscular dystrophy occurs when dystrophin is manufactured, although not in the normal form or amount. Because of this, people with Becker are more mildly affected and have a slower progression than people with Duchenne. As with Duchenne, Becker can be inherited from a parent or can be caused by a new or spontaneous mutation in the dystrophin gene. The symptoms of Becker can begin in childhood, the teenage years, or even later. PPMD’s mission and work extends to both Duchenne and Becker (both considered ‘dystrophinopathies’), but for simplicity we primarily refer to Duchenne.

Learn more about Genetic Causes