Muscular dystrophy (MD) is a group of more than 30 inherited genetic diseases that lead to progressive weakening and loss of control in muscles. The condition is caused by a mutation in the part of human genetic code responsible for building and maintaining muscle tissue. Typically, people inherit these genetic mutations from their parents, but they can also occur spontaneously at conception.
The most common type of MD is Duchenne muscular dystrophy, which is caused by a mutation in the gene responsible for producing a protein called dystrophin. Without dystrophin, muscle cells cannot maintain their structure. Patients with Duchenne MD typically develop the condition before age five and usually do not live past the age of 30. Other types of MD typically don’t cause muscular degeneration to the same extent as Duchenne, and the disease generally does not affect life expectancy in these patients.
How does muscular dystrophy affect the body?
The primary indicator of MD is progressive muscular deterioration. Each type of MD has a different age of onset, and different signs and symptoms. Duchenne, affecting roughly half of all MD patients, strikes boys almost exclusively. It typically presents itself when children are still learning to walk. Those affected will initially have difficulty standing up, walking and running. Eventually, boys will need a wheelchair to get around. MD may also affect the heart and respiratory muscles.
Becker MD is similar to Duchenne, but the symptoms are less severe and usually do not develop until age 10 or later. These patients may have heart or breathing issues. Although Becker patients are likely to experience muscle and joint pain, most do not need a wheelchair. Both types of MD affect predominantly affect boys because the mutated gene is situated on the X chromosome. (Girls have two X chromosomes, while boys have one X and one Y chromosome, so even if a girl inherits the faulty gene the other healthy gene can compensate for the mutation).
Facioscapulohumeral and myotonic MD usually appear in the teen years and in adulthood, with myotonic MD being the most common late-developing type of MD. Both conditions affect face and neck muscles.
How is muscular dystrophy diagnosed?
In addition to recognizing neuromuscular indicators of MD and reviewing family history, physicians may request several tests to definitively diagnose the disorder. Using a standard laboratory procedure, doctors can assess the blood levels of an enzyme, creatine kinase. A high concentration of creatine kinase indicates muscle damage. In such cases, the doctor may request an electromyography to measure muscular electrical activity. Similar to blood tests, this can be used to confirm a muscle disorder.
Genetic testing and muscle biopsies allow the physician to more clearly define a patient’s particular type of MD. These tests typically will not be done unless muscular generation is clearly causing the patient’s symptoms.
How is muscular dystrophy treated?
Although MD cannot be cured, several treatments can help to slow progression of the disease and minimize its symptoms. Physical therapy, respiratory therapy, speech therapy and orthopedic support devices can all help maintain muscle tone and functionality. Corticosteroids can increase muscle strength. Since these medications cause weight gain and osteoporosis, doctors usually don’t recommend their extended use. Exon skipping is a new therapy that shows promise as a method of limiting, and possibly reversing, muscle damage in Duchenne patients.
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