Alternative Names
Duchenne and Becker MD; DBMDl Duchenne/Becker muscular dystrophy; muscular dystrophy, Duchenne and Becker types; Muscular Dystrophy, Pseudohypertrophic
Symptoms & Characteristics
Muscular dystrophies are a group of genetic conditions characterized by progressive muscle weakness and wasting (atrophy).
The Duchenne and Becker types of muscular dystrophy primarily affect the skeletal muscles, which are used for movement, and the muscles of the heart. These conditions occur much more frequently in males than in females.
Duchenne and Becker muscular dystrophies have similar signs and symptoms and are caused by different mutations in the same gene. The two conditions differ in their severity, age of onset, and rate of progression.
- In people with Duchenne muscular dystrophy, muscle weakness tends to appear in early childhood and progress rapidly. Affected children may have delayed motor skills, such as sitting, standing, and walking. They are usually wheelchair-dependent by adolescence.
- The signs and symptoms of Becker muscular dystrophy are usually milder and exhibit a large range of variation. In most cases, muscle weakness becomes apparent later in childhood or adolescence and progresses at a much slower rate.
Both the Duchenne and Becker forms of muscular dystrophy are associated with a heart condition called dilated cardiomyopathy. This form of heart disease enlarges and weakens the heart (cardiac) muscle, preventing it from pumping blood efficiently. Dilated cardiomyopathy progresses rapidly and is life-threatening in many cases. In people with Duchenne muscular dystrophy, the signs and symptoms of cardiomyopathy typically appear in adolescence. The onset of cardiomyopathy in people with Becker muscular dystrophy is later, usually in early to mid-adulthood.
Treatment
There is currently no cure for muscular dystrophy. Early diagnosis, routine surveillance and treatment may help to manage some of the symptoms.
How Common Is It?
Duchenne and Becker muscular dystrophies together affect 1 in 3,500 to 5,000 newborn males. Between 400 and 600 boys in the United States are born with these conditions each year. Females are rarely affected by these forms of muscular dystrophy.
Genetics & Inheritance
Mutations in the DMD gene cause Duchenne and Becker muscular dystrophy.
This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
In about two thirds of cases, an affected male inherits the mutation from a mother who carries an altered copy of the DMD gene. The other one third of cases probably result from new mutations in the gene. In X-linked recessive inheritance, a female with one mutated copy of the gene in each cell is called a carrier. She can pass on the altered gene, but usually does not experience signs and symptoms of the disorder. Occasionally, however, females who carry a DMD mutation may have muscle weakness and cramping. These symptoms are typically milder than the severe muscle weakness and atrophy seen in affected males. Females who carry a DMD mutation also have an increased risk of developing heart abnormalities including dilated cardiomyopathy.
Genetic Testing
Clinical genetic testing for Duchenne and Becker muscular dystrophy is available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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