What is the definition of Duchenne Muscular Dystrophy?
Duchenne muscular dystrophy (DMD) affects the muscles, leading to muscle wasting that gets worse over time. DMD occurs primarily in males, though in rare cases may affect females. The symptoms of DMD include progressive weakness and loss (atrophy) of both skeletal and heart muscle. Early signs may include delayed ability to sit, stand, or walk and difficulties learning to speak. Muscle weakness is usually noticeable in early childhood. Most children with DMD use a wheelchair by their early teens. Heart and breathing problems also begin in the teen years and lead to serious, life threatening complications. DMD is caused by genetic changes (DNA variants) in the DMD gene. DMD is inherited in an X-linked recessive pattern and may occur in people who do not have a family history of DMD. Diagnosis of DMD is based on the symptoms, clinical exam, and the result of a biopsy to remove a small piece of muscle for examination under a microscope. The result of genetic testing may also help confirm the diagnosis. While there is no known cure for DMD, there are treatments that can help control symptoms.
Becker muscular dystrophy (BMD), a milder form of muscular dystrophy, is also caused by DNA variants in the DMD gene.
What are the alternative names for Duchenne Muscular Dystrophy?
- Muscular dystrophy, Duchenne
- Muscular dystrophy, pseudohypertrophic progressive, Duchenne type
What are the causes for Duchenne Muscular Dystrophy?
Duchenne muscular dystrophy (DMD) is occurs when the DMD gene is not working correctly. DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.
Different DNA variants in the DMD gene can cause a spectrum of disorders known as dystrophinopathies. The dystrophinopathies can range from very mild symptoms to the more severe symptoms seen in people with DMD. Other dystrophinopathies include Becker muscular dystrophy (BMD) and DMD-associated dilated cardiomyopathy (DCM).
What are the symptoms for Duchenne Muscular Dystrophy?
The following list includes the most common signs and symptoms in people with Duchenne muscular dystrophy (DMD). These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition.
Symptoms may include:
- Delayed motor development (taking longer to learn to sit, stand, or walk)
- Enlarged calf muscles (pseudohypertrophy)
- Muscle weakness that gets worse over time
- Toe walking or waddling gait
- Using hands to get up off the floor (Gower's maneuver)
- Progressive enlargement of the heart (cardiomyopathy)
The first symptoms of DMD usually occur in boys in early childhood, and include muscle weakness and clumsiness. Developmental milestones such as sitting and walking are often delayed. By the early teens, most boys with DMD are using a wheelchair. Breathing problems occur due to weakness of the diaphragm and the other muscles around the lungs. Scoliosis and tight joints (contractures) may develop as muscle loss gets worse. Breathing problems and progressive enlargement of the heart may become life-threatening. Learning and memory issues (cognitive impairment) may occur in some cases, but do not worsen as DMD progresses.
Is Duchenne Muscular Dystrophy an inherited disorder?
Duchenne muscular dystrophy (DMD) is inherited in an X-linked recessive pattern. X-linked means that the gene for the condition is located on the X-chromosome, one of the sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene is enough to cause the condition. X-linked recessive conditions affect males much more frequently than females. Females, who have one altered gene, are called carriers. While, most female carriers have no signs or symptoms of the condition, in rare cases, female carriers may experience some mild signs or symptoms.
A female who carries one X-linked gene alteration has a 50% or 1 in 2 chance of having a son with the condition and a 50% chance of having a daughter who is also a carrier. A male with an X-linked recessive condition cannot pass on the disorder to his sons, but all of his daughters will be carriers.
Sometimes a male child is the first person in a family with the condition. In this case, the gene alteration may have been inherited from the mother, or the alteration may have occurred by chance for the first time in the child (de novo).