| Duchenne muscular dystrophy | |
|---|---|
 | |
| Microscopic image of the calf muscle from a person with Duchenne muscular dystrophy. Cross section of muscle shows extensive replacement of muscle fibers by fat cells. | |
| Specialty | Medical genetics, pediatrics |
| Symptoms | Muscle weakness, trouble standing up, scoliosis[1][2] |
| Usual onset | Around age 4[1] |
| Causes | Genetic (X-linked recessive)[2] |
| Diagnostic method | Genetic testing[2] |
| Treatment | Physical therapy, braces, surgery, assisted ventilation[1][2] |
| Prognosis | Average life expectancy 26[3] |
| Frequency | 1 in 5,000 males at birth;[2] much rarer in females[4] |
Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys.[2] Muscle weakness usually begins around the age of four, and worsens quickly.[1] Muscle loss typically occurs first in the thighs and pelvis followed by the arms.[2] This can result in trouble standing up.[2] Most are unable to walk by the age of 12.[1] Affected muscles may look larger due to increased fat content.[2] Scoliosis is also common.[2] Some may have intellectual disability.[2] Females with a single copy of the defective gene may show mild symptoms.[2]
The disorder is X-linked recessive.[2] About two thirds of cases are inherited from a person's mother, while one third of cases are due to a new mutation.[2] It is caused by a mutation in the gene for the protein dystrophin.[2] Dystrophin is important to maintain the muscle fiber's cell membrane.[2] Genetic testing can often make the diagnosis at birth.[2] Those affected also have a high level of creatine kinase in their blood.[2]
Although there is no known cure, physical therapy, braces, and corrective surgery may help with some symptoms.[1] Assisted ventilation may be required in those with weakness of breathing muscles.[2] Medications used include steroids to slow muscle degeneration, anticonvulsants to control seizures and some muscle activity, and immunosuppressants to delay damage to dying muscle cells.[1]
DMD affects about one in 5,000 males at birth.[2] It is the most common type of muscular dystrophy.[2] The average life expectancy is 26;[3] however, with excellent care, some may live into their 30s or 40s.[2] Gene therapy, as a treatment, is in the early stages of study in humans.[2]