Muscular dystrophy (MD)
Muscular dystrophy (MD) is a group of rare inherited muscle diseases in which muscle fibers are unusually susceptible to damage. Muscles, primarily your voluntary muscles, become progressively weaker. In the late stages of muscular dystrophy, fat and connective tissue often replace muscle fibers. In some types of muscular dystrophy, heart muscles, other involuntary muscles and other organs are affected.
Nine major types of muscular dystrophy occur. The most common muscular dystrophies appear to be due to a genetic deficiency of the muscle protein dystrophin.
There's no cure, but medications and therapy can slow the course of the disease.
Signs and symptoms
Signs and symptoms vary according to the type of muscular dystrophy. In general, they may include:
Many specific signs and symptoms vary from form to form of MD. Each type is different in the age of onset, what parts of the body the symptoms primarily affect and how rapidly the disease progresses.
Duchenne's muscular dystrophy
Signs and symptoms of Duchenne's usually appear between the ages of 2 and 5. It first affects the muscles of the pelvis, upper arms and upper legs. By late childhood, most children with this form of muscular dystrophy are unable to walk. Most die by their late teens or early 20s, often from pneumonia, respiratory muscle weakness or cardiac complications. Some people with Duchenne's MD may exhibit curvature of their spine (scoliosis).
Becker's muscular dystrophy
The inability to relax muscles at will (myotonia) is found only in this type of muscular dystrophy. Although this form of MD can affect children, it often doesn't affect people until adulthood. It can vary greatly in its severity. Muscles may feel stiff after using them. Progression of this form of MD is slow. Besides myotonia, signs and symptoms of adult-onset myotonic dystrophy may include:
Rarely, infants have this form of muscular dystrophy, in which case it's called congenital myotonic dystrophy. The infant form is more severe, although infants with myotonic dystrophy don't experience myotonia. Signs in infants include:
The other major types of muscular dystrophy are rare. They include:
Limb-girdle muscular dystrophy
This form then progresses to the arms and legs, though progression is slow. Limb-girdle MD usually begins in the teen or early adult years.
Facioscapulohumeral muscular dystrophy
When someone with facioscapulohumeral MD raises his or her arms, the shoulder blades may stick out like wings. Progression of this form is slow, with some spurts of rapidly increasing weakness. Onset usually occurs during the teen to early adult years.
Congenital muscular dystrophy
This form is apparent at birth and progresses slowly. A more severe form of congenital MD called Fukuyama type congenital muscular dystrophy may involve severe mental and speech problems as well as seizures.
Oculopharyngeal muscular dystrophy
Distal muscular dystrophy
Emery-Dreifuss muscular dystrophy
Emery-Dreifuss MD usually begins in the childhood to early teen years and progresses slowly.
Muscular dystrophy is a general term for a group of inherited diseases involving a defective gene. Each form of muscular dystrophy is caused by a genetic mutation that's particular to that type of the disease.
Duchenne's and Becker's muscular dystrophies are passed from mother to son through one of the mother's genes in a pattern called X-linked recessive inheritance. Boys inherit an X chromosome from their mother and a Y chromosome from their father. The X-Y combination makes them male. Girls inherit two X chromosomes, one from their mother and one from their father. The X-X combination determines that they are female.
The defective gene that causes Duchenne's and Becker's muscular dystrophies is located on the X-chromosome. Women who have the defective gene that causes these muscular dystrophies are simply carriers and exhibit no signs or symptoms of the disease. The disease can "skip" a generation until another son inherits the defective gene on the X-chromosome. In some cases of Duchenne's and Becker's muscular dystrophies, the disease arises from a new mutation in a gene rather than from an inherited defective gene.
Myotonic dystrophy is passed along in a pattern called autosomal dominant inheritance. If either parent carries the defective gene for myotonic dystrophy, there's a 50 percent chance the disorder will be passed along to a child.
Some of the less common types of muscular dystrophy are passed along in the same inheritance pattern that marks Duchenne's and Becker's muscular dystrophies. Other types of muscular dystrophy can be passed on from generation to generation and affect males and females equally. Still others require a defective gene from both parents.
When to seek medical advice
Duchenne's muscular dystrophy occurs almost exclusively in boys, although it can occur in girls. Your young child may have difficulty walking, running, getting up or climbing the stairs, or may appear clumsy and fall often. These may be early indications of muscular dystrophy. A child with MD may learn to walk later than other children do and may exhibit signs of muscle weakness between the ages of 2 and 5. By school age, a child with MD may walk unsteadily and on the toes or balls of his feet. Duchenne's MD usually results in children losing the ability to walk between the ages of 7 and 12.
If you're concerned about your child's motor abilities, clumsiness or muscle strength and development, see your doctor. Once muscular dystrophy is diagnosed, medications and physical therapy can help slow its progression.
Because muscular dystrophies are inherited disorders, genetic counseling may be helpful if you're considering having children and to assess the risk of the disease in other family members.
Screening and diagnosis
A careful review of your family's history of muscle disease can help your doctor reach a diagnosis. In addition to a medical history review and physical examination, your doctor may rely on the following in diagnosing muscular dystrophy:
There's currently no cure for any form of muscular dystrophy. Research into gene therapy may eventually provide treatment to stop the progression of some types of muscular dystrophy. Current treatment is designed to help prevent or reduce deformities in the joints and the spine and to allow people with MD to remain mobile as long as possible. Treatments may include various types of physical therapy, medications, assistive devices and surgery.
One goal of physical therapy is to provide regular range of motion exercises to keep your joints as flexible as possible, delaying the progression of contractures, and reducing or delaying curvature of your spine. Using hot baths (hydrotherapy) also can help maintain range of motion in joints.
For family members of people with muscular dystrophy, coping with the illness involves a major commitment of physical, emotional and financial effort. The disease presents challenges in the classroom, in the home and in all aspects of life.
In dealing with a disease such as muscular dystrophy, support groups can be a valuable part of a wider network of social support that includes health care professionals, family, friends and place of religious worship.
Support groups bring together people, family and friends who are coping with the same kind of physical or mental health challenge. Support groups provide a setting in which people can share their common problems and provide ongoing support to one another.
Ask your doctor about self-help groups that may exist in your community. Your local health department, public library, telephone book and the Internet also may be good sources to locate a support group in your area.