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 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
- Breathing problems
- Scoliosis: A lateral, or sideways, curvature and rotation of the back bones (vertebrae), giving the appearance that the person is leaning to one side
- Gastrointestinal problems
- Obesity
The most common forms of muscular dystrophy are Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy. The two forms are very similar, but Becker muscular dystrophy is less severe than DMD. Girls are rarely affected by either of these two forms of muscular dystrophy.
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.
What are the symptoms of muscular dystrophy?
Muscular dystrophy can be diagnosed at any age. The Duchenne form of muscular dystrophy is usually diagnosed in children between 3 and 6 years of age. Early signs of muscular dystrophy include a delay in walking, difficulty rising from a sitting or lying position, and frequent falling, with weakness typically affecting the shoulders and pelvic muscles 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
- Leg pain
- Tiring quickly with exertion
- Facial weakness
- Inability to close eyes or whistle
- Shoulder and arm weakness
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 then walks his or her hands up their legs to brace themselves as they rise to a standing position.
In addition, children with muscular dystrophy often have very large calves 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 doctor 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 doctor 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. These include genetic blood tests.
- Muscle biopsy. A test used to confirm diagnosis if genetic testing is negative. A small sample of muscle tissue is taken and examined under a microscope.
- Electromyogram (EMG) and nerve conduction studies (NCS). A 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 may detect heart muscle damage.
- Echocardiogram (echo). An ultrasound of the heart that can detect dilation or thickening of the heart muscle.
Treatment for muscular dystrophy
Specific treatment for muscular dystrophy will be determined by your child's doctor 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. There are medicines available for some forms of muscular dystrophy that can slow muscle weakening.
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 nonsurgical or surgical. Nonsurgical interventions may include:
- Physical therapy and occupational therapy
- Positioning aids used to help the child sit, lie, or stand
- Braces and splints used to prevent deformity, promote support, or provide protection
- Medications
- 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
- Joint contractures
- Maintaining the child's ability to sit or stand
Gene Therapy for Duchenne Muscular Dystrophy
Gene therapy for DMD is designed to induce production of a shortened but functional version of dystrophin, known as a micro-dystrophin protein.
Long-term outlook for a child with muscular dystrophy
Muscular dystrophy is a progressive condition that needs life-long management to prevent or minimize deformity and complications. Walking and sitting often become more difficult over time. In Duchenne muscular dystrophy, usually by the age of 12 or 13 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 in Duchenne muscular dystrophy.
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 can be an important resource, both financially and emotionally, for parents of children with muscular dystrophy.
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Reviewed by John Brandsema, MD