What is Duchenne/Becker Muscular Dystrophy?
Duchenne and Becker Muscular Dystrophy are inherited disorders called “Dystrophinopathies” that cause progressive breakdown and weakness of both skeletal and heart muscle. In Duchenne Muscular Dystrophy, the muscle weakness usually begins around 3 to 5 years of age and worsens over time. By the teenage years, the muscle degeneration and weakness also starts to involve the muscles of the lungs and heart. In Becker Muscular Dystrophy, the signs and symptoms are milder and begin later in childhood. For both conditions, it is more common for boys to be affected than girls. Children and adults with Duchenne/Becker Muscular Dystrophy need physical and occupational therapy and lifelong medical treatment. Most boys with Duchenne Muscular Dystrophy will need a wheelchair by their mid to late teenage years; boys with Becker Muscular Dystrophy are often in their late teens or early adulthood before they need a wheelchair. A variable degree of intellectual disability may occur and is more common in children with Duchenne than in children with Becker. Presently there is no cure for Duchenne/Becker Muscular Dystrophy. With current medical treatments, survival is common into the 20s and 30s with Duchenne Muscular Dystrophy and into the 40s with Becker Muscular Dystrophy. Some males have a separate form of Dystrophinopathy called DMD-Associated Dilated Cardiomyopathy, which does not include skeletal muscle weakness. DMD-Associated Dilated Cardiomyopathy causes progressive heart problems where one or more chambers of the heart dilate, the heart muscle weakens, and congestive heart failure occurs. Symptoms typically start between the ages of 20 and 40 years and lifespan is shortened. About 1 in every 3500 males is born with Duchenne Muscular Dystrophy and about 1 in every 18,500 boys is born with Becker Muscular Dystrophy. DMD-Associated Dilated Cardiomyopathy is rare.
Some female carriers develop heart problems such as dilated cardiomyopathy and some have other symptoms of Duchenne/Becker Muscular Dystrophy such as mild to moderate muscle weakness. In rare cases, female carriers may have more serious symptoms.
What causes Duchenne/Becker Muscular Dystrophy?
Duchenne/Becker Muscular Dystrophy is caused by a change, or mutation, in the DMD gene. This mutation causes the gene to not work properly or not work at all. When this gene does not work correctly, it leads to a lack of dystrophin, a protein normally found in muscle cells. Muscle cells in the skeleton and heart that don’t have enough dystrophin gradually stop working, leading to the symptoms described above. It is sometimes but not always possible to tell just by the mutation whether a boy will have the Duchenne or Becker form of this condition.