ORTHOPAEDICS :: Congenital and Hereditary Disorders
What is muscular dystrophy?
Muscular dystrophy (MD) is a broad term that describes a genetic (inherited) disorder of the muscles. Muscular dystrophy causes the muscles in the body to become very weak. The muscles break down and are replaced with fatty deposits over time.
Other health problems commonly associated with muscular dystrophy include the following:
The most common form of muscular dystrophy is called Duchenne muscular dystrophy (DMD). Duchenne muscular dystrophy usually affects only males. It occurs in one out of 3,500 live male births. Muscular dystrophy rarely affects girls, but when it does, the condition is normally not as severe.
What causes muscular dystrophy?
Duchenne muscular dystrophy is a genetic disease which means it is inherited. Our genes determine our traits, such as eye color and blood type. Genes are contained in the cells of our bodies on stick-like structures called chromosomes. There are normally 46 chromosomes in each cell of our body, or 23 pairs. The first 22 pairs are shared in common between males and females, while the last pair determine gender and are called the sex chromosome pair: females have two X chromosomes, while males have one X and one Y chromosome.
Duchenne muscular dystrophy is caused by an X-linked recessive gene. "X-linked" means that the gene causing the trait or the disorder is located on the X chromosome. Genes on the X chromosome can be recessive or dominant, and their expression in females and males is not the same because the genes on the Y chromosome do not exactly pair up with the genes on the X. X-linked recessive genes are expressed in females only if there are two copies of the gene (one on each X chromosome). However, for males there only needs to be one copy of an X-linked recessive gene in order for the trait or disorder to be expressed. For example, a woman can carry a recessive gene on one of the X chromosomes unknowingly, and pass it on to a son, who will express the trait or disease.
Therefore, half of the daughters have the gene and can pass it to the next generation. The other half do not have the gene and therefore cannot pass it on. Half of the sons do not have the gene and cannot pass it on. The other half of the sons have inherited the gene and will express the trait or disorder (in this case, DMD).
In Duchenne muscular dystrophy (DMD), 33 percent of all cases are thought to be new mutations in the family (not inherited from the mother).
What are the symptoms of muscular dystrophy?
Muscular dystrophy is usually seen in children before the age of 5, with weakness typically affecting the shoulder and pelvic muscle as one of the initial symptoms. The following are the most common symptoms of muscular dystrophy. However, each child may experience symptoms differently. Symptoms may include:
A tell-tale clinical characteristic for Duchenne muscular dystrophy (DMD) is Gowers' sign. Children with Duchenne muscular dystrophy find it very hard to get up from a sitting or lying position on the floor. They first pull up to their hands and knees. The child walks his/her hands up their legs to brace themselves as they rise to a standing position.
Another classic symptom of muscular dystrophy is known as the "slip through" symptom. Your child's physician puts his/her hands around the sides of the child's chest, right up under the arms. As the child is lifted up, the shoulders weaken and move upward, almost allowing the child to slip through your child's physician's hands.
In addition, children with muscular dystrophy often have very large calf muscles due to the large amounts of fatty deposits that are replacing muscle.
The symptoms of muscular dystrophy may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
How is muscular dystrophy diagnosed?
The diagnosis of muscular dystrophy is made with a physical examination and diagnostic testing by your child's physician. During the examination, your child's physician obtains a complete prenatal and birth history of the child and asks if other family members are known to have muscular dystrophy.
Diagnostic tests for muscular dystrophy may include:
Treatment for muscular dystrophy:
Specific treatment for muscular dystrophy will be determined by your child's physician based on:
To date, there is no known treatment, medicine, or surgery that will cure muscular dystrophy, or stop the muscles from weakening. The goal of treatment is to prevent deformity and allow the child to function as independently as possible.
Since muscular dystrophy is a life-long condition that is not correctable, management includes focusing on preventing or minimizing deformities and maximizing the child's functional ability at home and in the community.
Management of muscular dystrophy is either non-surgical or surgical. Non-surgical interventions may include:
Surgical interventions may be considered to manage the following conditions:
Long-term outlook for a child with muscular dystrophy:
Muscular dystrophy is a progressive condition that needs life-long management to prevent deformity and complications. Walking and sitting often becomes more difficult as the child grows. Usually by the age of 12, the child needs a wheelchair because the leg muscles are too weak to work. Heart or lung problems often occur by the late teenage years or into the early 20s.
The interdisciplinary healthcare team will work with your family to improve your child's functional outcomes and to provide support as you learn to care for your child's needs.
The Muscular Dystrophy Association (MDA) can be an important resource, both financially and emotionally, for parents of children with muscular dystrophy.
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It is important to remember the health information found on this website is for reference only not intended to replace the advice and guidance of your healthcare provider. Always seek the advice of your physician with any questions you may have regarding a medical condition. If you think you may have a medical emergency, call your physician or 911 immediately.
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