Muscular dystrophy is a genetic brain disease that affects the muscles and causes them to weaken. This group of disorders includes more than 30 different genetic diseases, which can vary based on when symptoms begin, the type and severity of muscle weakness, how quickly the disease progresses, and the chances of passing along the genetic disease to children or grandchildren.
The most common type of muscular dystrophy is Duchenne muscular dystrophy (DMD), which affects children. DMD primarily affects boys: One in 3,500 males worldwide develop DMD. Girls in affected families can also inherit and pass on the gene for DMD. DMD is not more common among any specific race or ethnicity.
DMD is caused by a genetic defect that prevents the production of a protein called dystrophin, which helps maintain muscle structure and strength. When this protein is missing, the muscle degenerates and becomes inflamed, starting an immune response that leads to further inflammation and muscle weakness—a continuous, destructive cycle.
Other common types of muscular dystrophy include facioscapulohumeral muscular dystrophy, which begins in the teenage years and progresses more slowly, and myotonic dystrophy, which is the most common form to affect adults and causes cataracts, heart abnormalities, and difficulty relaxing muscles.
Number of males worldwide who develop Duchenne muscular dystrophy (DMD)
Average age of diagnosis
Muscle weakness is the primary sign of muscular dystrophy, and its progression can affect a person’s ability to move, walk, and breathe. Symptoms can start at different ages and vary in severity and how fast they progress.
In the case of DMD, symptoms generally start between ages 3 and 5. Muscle weakness typically begins in the upper arms and upper legs and can spread to the heart, lungs, throat, stomach, intestines, and spine. DMD’s rapid progression of muscle weakness means patients are often unable to walk by age 12 and can eventually require a respirator to breathe.
The progression of the disease can vary depending on the type of muscular dystrophy. Some forms cause a rapid progression of muscle weakness, while others result in a slower progression over a normal lifespan. Symptoms also vary from mild to severe, including losing the ability to walk.
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