Duchenne muscular dystrophy is a severe recessive X-linked form of muscular dystrophy characterized by rapid progression of muscle degeneration.
Primarily affecting males, Duchenne muscular dystrophy (DMD) is defined as a progressive muscle disorder caused by the lack of functional dystrophin protein. Dystrophin is critical to the structural stability of skeletal, diaphragm, and heart muscles. Patients with DMD, the more severe form of the disorder, lose the ability to walk as early as age 10 and experience life-threatening lung and heart complications in their late teens and twenties. It is estimated that a nonsense mutation is the cause of DMD in approximately 13% of patients, or approximately 2,000 patients in the United States and 2,500 patients in the European Union.
Duchenne Muscular Dystrophy (DMD) is one of the types of muscular dystrophy, a group of genetic, degenerative diseases primarily affecting voluntary muscles, and caused by an absence of dystrophin, a protein that helps keep muscle cells intact.
Duchenne muscular dystrophy is a severe recessive X-linked form of muscular dystrophy characterized by rapid progression of muscle degeneration, eventually leading to pain, loss in ambulation, and death. This affliction affects one in 3500 males, making it the most prevalent of muscular dystrophies. In general, only males are afflicted, though females can be carriers. The disorder is caused by a mutation in the gene DMD, located in humans on the X chromosome.
Symptoms usually appear in male children before age 6 and may be visible in early infancy.
Progressive proximal muscle weakness and pain in the legs and pelvis associated with a loss of muscle mass is observed first. Eventually this weakness spreads to the arms, neck, and other areas.
Early signs may include pseudohypertrophy (enlargement of calf muscles), low endurance, and difficulties in standing unaided or inability to ascend staircases.
As the condition progresses, muscle tissue experiences wasting and is eventually replaced by fat and fibrotic tissue (fibrosis).
By age 10, braces may be required to aide in walking but most patients are wheelchair dependent by age 12.
Later symptoms may include abnormal bone development that lead to skeletal deformities, including curvature of the spine. Due to progressive deterioration of muscle, loss of movement occurs eventually leading to paralysis. Intellectual impairment may or may not be present but if present, does not progressively worsen as the child ages.
The average life expectancy for patients afflicted with DMD varies from early teens to age mid 30s. There have been reports of DMD patients surviving past the age of 40 and even 50.
A muscle biopsy (taking a sample of muscle) for dystrophin studies can be done to look for abnormal levels of dystrophin in the muscle. The dystrophin protein can be visualized by staining the muscle sample with a special dye that allows you to visualize the dystrophin protein. A muscle which has average amounts of dystrophin will appear with the staining technique as though there is caulking around the individual muscles cells as though it is holding them together like window panes, while a boy with Duchenne will have an absence of dystrophin and appear to have absence of the caulking around the muscle cells. Some individuals can be found to have an intermediate amount of the dystrophin protein, often these boys are classified as having Becker muscular dystrophy. This is the gold standard for the diagnosis of DMD.
There is no known cure for Duchenne muscular dystrophy. Treatment aims to control symptoms to maximize quality of life and reduce duchenne muscular dystrophy pain. Gene therapy may become available in the future.
Activity is encouraged. Inactivity (such as bedrest) can worsen the muscle disease. Physical therapy may be helpful to maintain muscle strength and function. Orthopedic appliances (such as braces and wheelchairs) may improve mobility and the ability to care for yourself.
Update: Recent research shows Losartan, a currently available drug used for treating hypertension, to be effective in halting the progress of the disease in mice that were genetically engineered to have Duchenne's. Human trials are in planning.