Muscular Dystrophy (MD) refers to a group of genetic diseases that cause progressive weakness and degeneration of voluntary muscles that control movement. In some forms of MD, involuntary muscles (i.e., heart muscles) may be affected as well. MD is caused by flaws in muscle protein genes, which can cause either the protein to be produced incorrectly or in the wrong amount.
MD is generally inherited in one of three genetic patterns: autosomal dominant, autosomal recessive, and X-linked recessive. When MD is inherited by the autosomal dominant pattern, it is caused by an affected gene inherited by only one parent. With autosomal recessive diseases, the faulty gene is inherited by both parents. Finally, the X-linked recessive cases are caused by faulty genes on the X chromosome (a male has an X and a Y chromosome and a female has two X chromosomes). Females tend to be more mildly affected than males because females have a second X chromosome to compensate for the defective gene on the affected X chromosome.
There are, however, cases where there is no history of illness in the family. These cases are caused by spontaneous mutations, where the defect in the gene is not inherited, but occurs for the first time in the child.
Features and Characteristics
There are nine major forms of MD which differ in terms of severity, age of onset, muscles first and most affected, the rate of progression, and the way the disorder is inherited.
Duchenne Muscular Dystrophy (DMD)
DMD is the most common form of childhood MD. The symptoms are typically first seen between the ages of 2-6 years. Frequent falling, difficulty getting up, waddling gait, and enlarged calf muscles are often the early signs. DMD is an X-linked recessive disorder found exclusively in males. The pelvis, upper arms, and upper legs are the first muscles affected. Mild mental retardation is found in some boys with DMD. The progression of DMD is slow, however, by age 12, the child may require a wheelchair. Breathing becomes affected during the later stages, which can be treated with antibiotics and respiratory treatment. Severe respiratory and heart problems are found in the final stages, usually in the boys teens or early 20s. The gene that causes DMD was identified in 1986, which makes gene therapy a potential form of treatment for boys with DMD.
Becker Muscular Dystrophy (BMD)
The signs and symptoms of BMD are similar to DMD, however, they appear later in life and the progression is slower. Both BMD and DMD have defects in the same gene (although, a different defect), which offers hope for those with BMD as well in terms of gene therapy. BMD is an X-linked recessive disease found exclusively in males. The muscles first affected are the upper arms, upper legs, and pelvis. The age of onset is 2-16 years of age, and the ability to walk usually remains until the individual reaches his 30s.
Congenital Muscular Dystrophy (CMD)
CMD includes several different congenital diseases that can be noted at birth. CMD is an autosomal recessive disorder that occurs in both males and females. The progression is slow and the symptoms vary depending on the type of CMD.
Limb-Girdle Muscular Dystrophy (LGMD)
LGMD can be an autosomal recessive or autosomal dominant disorder. It is found in both males and females and usually first appears in adolescence or early childhood. LGMD causes weakness that begins in the hips and moves to the shoulders, and then progresses to include the arms and legs. Although progression is slow, within 20 years of onset, walking becomes nearly impossible.
Myotonic Muscular Dystrophy
This form of MD, also known as Steinerts disease, is the most common adult form of MD, although, it can appear in early childhood. Myotonic MD results in myotonia, a symptom similar to a spasm or stiffening of a muscle. It typically is a result of a gene flaw on chromosome 19, which causes muscle weakness, and can affect the central nervous system, heart, gastrointestinal tract, eyes, and endocrine glands. Many individuals with myotonic MD require more sleep than usual and mild mental retardation and an emotional indifference may be found. It is an autosomal dominant type of MD and the muscles first affected are the face, feet, hands, and front of neck. The progression is considered slow.
Facioscapulohumeral Muscular Dystrophy (FSH)
FSH is an autosomal dominant disorder, affecting both males and females, which first appears in the teen years or early adulthood. The early signs of FSH are a forward sloping of the shoulders and difficulty raising the arms over the head and closing the eyes. The weakness then typically spreads to the abdominal muscles, feet, upper arms, pelvic area, and arms. FSH is a slow progressing disease and there is a wide range of severity, from very mild to very severe (inability to walk, chew, swallow, and speak). Approximately half of those affected by FSH will be able to continue walking throughout their lives.
Emery-Dreifuss Muscular Dystrophy (EDMD)
EDMD is a rare form of MD and is an X-linked recessive disorder that occurs only in males. The disease appears in childhood or the early teen years and the upper arms and lower legs are the first muscles to be affected. The progression is slow and the skeletal muscle weakness is often times less severe than the other dystrophies. Life threatening heart problems are common in individuals with EDMD, however, they may be treated with a cardiac pacemaker.
Distal Muscular Dystrophy (DD)
DD also includes several different diseases which all lead to distal wasting of forearms, hands, lower legs, and feet. The onset of DD is in adulthood and is an autosomal recessive and autosomal dominant disorder, with both males and females being affected. In general, the DDs progress slowly and are not as severe as other forms of MD.
Oculopharyngeal Muscular Dystrophy (OPMD)
OPMD is an autosomal dominant disorder that occurs in males and females with an onset often in the individuals 40s, 50s, or 60s. It usually begins with drooping of the eyelids, and is followed by other signs of facial weaknesses. Swallowing problems also occur, which often times leads to choking and pneumonia. This form of MD is linked to a defect on chromosome 14.
A diagnosis is typically made by an evaluation of the childs medical history and by performing a physical examination. The physician determines the type of MD based on when the muscle weakness first occurred, its severity, and which muscles are affected. There are, however, four tests that a physician may consider to help confirm the diagnosis: 1) A muscle biopsy may be taken to look for deficient, abnormal or absent muscle proteins, which may help determine which type of MD the individual has. 2) An electromyogram (EMG) may also be completed to measure the electrical impulses coming from the muscles that appear to be most affected. 3) A test to measure the nerve conduction velocity is often performed to determine whether the nerves are functioning correctly. 4) Blood enzyme tests are often useful in that degenerating muscles often leak enzymes into the blood, therefore, making elevated levels of enzymes a possible sign of MD.
At this time, there is no cure for MD, however, gene therapy may prove to be a viable treatment in the near future. Scientists are currently working on inserting healthy genes into individuals with Duchenne and Becker muscular dystrophies. Researchers are also working on locating the gene and protein abnormalities that cause other forms of MD so that gene therapy infusions become an option for individuals with the other forms of MD as well.
Until a cure becomes available, there are several types of treatments used for minimizing the symptoms of MD:
- Physical therapy and exercise - For joint contractures and scoliosis, an exercise program and physical therapy can minimize the affects.
- Devices - The use of devices such as canes, walkers, or wheelchairs can help maintain independence as long as possible.
- Surgery - Surgery may be an option to relieve muscle shortening.
- Respiratory Care - This treatment becomes more important as the disease progresses. Deep breathing and coughing with the aid of a special device may be recommended.
- Medication - Corticosteroids can slow muscle destruction in Duchenne MD. The side effects of this medication, however, can be very serious including bone loss, skin infections, high blood pressure and weight gain.
- Cardiac Pacemaker - This device may be necessary for those with Emery-Dreifuss MD due to the cardiac problems often seen with this form of MD.
Aside from the medical and therapeutic measures mentioned above, there are educational considerations as well. A child with MD should receive the same education as any other child. However, the decision of whether to place a child with MD in a regular education setting versus a special education setting should be based on each individual child.
Children with MD may not have any noticeable signs of the disease when entering the school system at age 5 years. However, since MD is a progressive disorder, the school should allow any adaptions or equipment necessary to provide the child with an appropriate education. Sometimes, a teachers aide may be required for the child to benefit from an education in a mainstream setting and to receive the appropriate care. However, it is important to ensure that the child is still integrated in the classroom and not isolated with the aide.
Consultation with an occupational therapist may be necessary to ensure that the child is receiving proper adaptations and equipment. An individual exercise program should be carried out in the school setting and children should be encouraged to continue participating in peer group activities as long as they do not over-extend themselves. A physical therapist should recommend an exercise program for the child and have it followed through in P.E. at school. Also, often times, as a child becomes less mobile, they become less involved with their peers. Schools can help the child with MD by encouraging him to join after-school clubs.
What to Expect
With the advances in medicine, children with MD are living further into adulthood than ever before, however, the type of MD determines the expected prognosis of the affected individual. For example, individuals with DMD, at this point, are said to live into their mid 20s, whereas, those with BMD have a life expectancy of mid to late adulthood. Fortunately, this may all change one day soon, as researchers are preparing to begin gene therapy trials in the Fall of 1999 and are closer to finding a cure than ever before.
If you are interested in meeting other parents and individuals who are involved in raising a child with Muscular Dystrophy, the following listserv is available:
MD-list - To subscribe, send an e-mail message to MDemail@example.com. Leave the subject field blank and in the body of the message, type: "Subscribe" (without the quotes). You will then receive a confirmation. Also, the following newsgroup is available: alt.support.musc-dystrophy.
For more information on Muscular Dystrophy, please visit these helpful sites:
- The Muscular Dystrophy Association http://www.mdausa.org
- Parent Project for Muscular Dystrophy Research http://www.parentdmd.org/index.htm
- National Institutes of Health http://www.ninds.nih.gov/patients/Disorder/md/md.htm#description
- Muscular Dystrophy Family Foundation http://www.mdff.org/index.html
- MD Net International Support Network http://www.mda.org.au/services/mdcontac.html
- Muscular Dystrophy Campaign http://www.muscular-dystrophy.org/largetext/start/home.html
- Muscular Dystrophy Association of Canada http://www.mdac.ca
- International Myotonic Dystrophy Organization http://www.myotonicdystrophy.org
The Disorder Zone has been created for educational purposes only and is not intended to serve as medical advice. The information provided in The Zone should not be used for diagnosing or treating a health problem or disease. It is not a substitute for professional care. If your child has any health concerns, please consult your health care provider.
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