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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:
- Heart problems
- Respiratory (breathing) problems
- Scoliosis (a condition that causes the back bones to curve)
There are several types of muscular dystrophy. The most common form of muscular dystrophy is called Duchenne's muscular dystrophy (DMD). Duchenne's 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's 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's 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's muscular dystrophy (DMD), one-third 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:
- Clumsy movement
- Difficulty climbing stairs
- Frequently trips and falls
- Unable to jump or hop normally
- Tip toe walking
A tell-tale clinical characteristic for muscular dystrophy is Gowers' sign. Children with 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 healthcare provider places 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 the 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 healthcare provider 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:
- Blood tests-- creatine kinase (CK) level as well as other tests
- Muscle biopsy -- the primary test used to confirm diagnosis; a small sample of muscle tissue is taken and examined under a microscope
- Electromyogram (EMG) -- test to check if the muscle weakness is a result of destruction of muscle tissue rather than nerve damage
- Electrocardiogram (ECG or EKG) -- a test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle damage
Treatment for muscular dystrophy:
Specific treatment for muscular dystrophy will be determined by your child's healthcare provider based on:
- Your child's age, overall health, and medical history
- The extent of the condition
- The type of condition
- Your child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the condition
- Your opinion or preference
To date, there is no known treatment, medicine, or surgery that will cure muscular dystrophy, or stop the muscles from weakening. Therefore, 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 conservative (non-surgical) or surgical. Non-surgical interventions may include:
- Physical therapy
- Positioning aids - used to help the child sit, lie or stand
- Braces and splints - used to maximize development gains, promote support or provide protection
- Nutritional counseling
- Psychological counseling
Surgical interventions may be considered to manage the following conditions:
- Scoliosis (a sideways curvature of the back bones) associated with muscular dystrophy
- Maintaining the child's ability to sit or stand
Long-term outlook for a child with muscular dystrophy:
Muscular dystrophy is a progressive condition that needs life-long management to maintain functional abilities and prevent 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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