One of the nine types of muscular dystrophy, Duchenne muscular dystrophy (DMD) is a genetic condition characterized by progressive weakening of voluntary muscles that leads to death. DMD worsens more rapidly than other types of muscular dystrophy. It is also the most common form of muscular dystrophy: according to the Centers for Disease Control and Prevention, an estimated one of every 5,600 to 7,700 males between five and 24 years of age have DMD. (CDC)
The condition is often associated with young people because symptoms begin in early childhood and those with DMD usually die in early adulthood.
DMD is a genetic disease. Those who inherit it have a defective gene related to a muscular protein called dystrophin. This protein keeps muscle cells intact, and its absence causes rapid muscular deterioration as a child with DMD grows.
A family history of DMD is a risk factor, but the condition may be inherited without a known family history because it can be carried silently. This means family members carry a copy of the defective gene, but it does not cause DMD in those individuals. The gene is sometimes carried for generations before affecting a child.
Males are more likely to suffer from DMD than females. Children of both genders who are born to a mother who carries the defective gene each have a 50 percent chance of inheriting the defect. However, girls who inherit the gene will be asymptomatic carriers, and boys will present with symptoms.
Symptoms generally start to appear between age 2 and 6. Many sufferers develop normally during infancy and early childhood. DMD symptoms may include:
- difficulty walking or loss of ability to walk
- enlarged calves
- learning disabilities (in about one-third of affected individuals)
- lack of motor skills development
- rapidly worsening weakness in the legs, pelvis, arms, and neck
Muscular dystrophy may be suspected during routine wellness exams. The pediatrician and parents may notice muscle weakening and lack of coordination. Blood tests and muscle biopsies can confirm a diagnosis of DMD. The blood test used to reach this diagnosis is called a creatine phosphokinase test. When muscles deteriorate, they release a large amount of creatine phosphokinase enzyme into the blood. If high levels are detected, muscle biopsies or genetic tests will determine the type of muscular dystrophy.
There is no cure for DMD. Treatment is meant to mitigate symptoms and extend life expectancy.
Children with DMD often lose the ability to walk and require a wheelchair by about age 12. Leg bracing may be used to extend the amount of time a child is able to walk independently. Regular physical therapy keeps the muscles in the best possible condition. Steroid treatments may also be prescribed to prolong muscle function.
Weakening muscles can cause ailments such as scoliosis, pneumonia, and abnormal heart rate. These must be treated and monitored as they occur.
Lung function begins to deteriorate in the late stages of the disease, and a ventilator may be used to prolong life.
DMD is a fatal condition. Most sufferers pass away during their twenties, but with diligent care, some survive into their thirties. In the later stages of the disease, most sufferers are completely disabled and require full-time care.
The condition is degenerative. The need for medical care increases as the condition worsens. As symptoms begin to appear between age 2 and 6, the child will usually need regular monitoring by a team of medical professionals. As the final stages of the disease emerge during the teen and young-adult years, the sufferer may need to be hospitalized or receive hospice care.
DMD can’t be prevented before conception because it is inherited from the mother. Geneticists are researching technology that may be able to prevent the defect from being passed on, but no successful cure has been discovered.
Genetic testing prior to conception can determine whether a couple faces an increased risk of bearing children with DMD. Tests done on pregnant women can diagnose DMD in utero with about 95 percent accuracy.