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Duchenne Muscular Dystrophy

Genetic muscle disorder

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Updated October 11, 2008

Voluntary muscles are affected by Duchenne MD

Voluntary muscles are affected by Duchenne MD

Photo © A.D.A.M.
Duchenne muscular dystrophy (DMD) is one of nine types of muscular dystrophy, a group of genetic disorders that affect the use of voluntary muscles in the body. Duchenne MD is inherited as an X-linked disorder. Because of the way it is inherited, Duchenne MD primarily affects boys. Girls can inherit the gene for DMD but not have any symptoms of the disease.

Duchenne MD affects approximately 1 in every 3,500 live male births (about 20,000 new cases each year). It affects children of all ethnic backgrounds. The gene for DMD causes an absence of dystrophin, a protein that helps keep muscle cells intact. This means that muscle cells are easily damaged and become weak over time.

Symptoms

A boy with Duchenne MD usually develops normally as an infant. The symptoms of DMD typically begin between ages 2 and 6. The affected child may:
  • have difficulty walking, running, or climbing stairs due to weakness in the legs and pelvis
  • struggle to lift the head, or has a weak neck
  • need help getting up from the floor
  • walk with his legs apart
  • stand and walk with his chest and stomach stuck out (or has a sway back)
  • use the Gower maneuver to get up from the floor (walks his hands up his legs instead of standing straight up, due to weak leg muscles)
Duchenne MD eventually affects all the muscles in the body, including the heart and breathing muscles, so as the child grows older symptoms may include:
  • fatigue
  • difficulty breathing
  • heart problems due to an enlarged heart
  • loss of ability to walk by age 12
  • weakness in the arms and hands

Diagnosis

Diagnosis of Duchenne MD is usually based on the development of the symptoms in the child’s preschool years. Parents or teachers begin to notice the boy having difficulty climbing stairs or keeping up with other children.

In the early stages of DMD, a blood test for creatine kinase (CK or CPK) may show elevated levels that are 10 to 100 times normal. This test shows that muscle damage is occurring but does not confirm the diagnosis. Genetic testing — looking for the presence of the DMD gene — is the best way to confirm the diagnosis. Once a child is known to have DMD, other family members can be tested to see who else may also have the gene.

Treatment

Although much research about Duchenne MD is being done, there is no cure yet, or a way to stop the disease from getting worse over time. The medication prednisone can slow muscle loss, improve strength, and help restore energy, but it has serious side effects when taken for a long time. Medication may need to be taken if heart problems are present. Physical and occupational therapy are helpful in maintaining flexibility and preventing the weakened muscles from contracting. Aerobic activity such as swimming is very good for boys with DMD. Speech therapy may be needed if the child is having difficulty speaking or communicating.

As the disease progresses, the boy will need adaptive devices such as braces and a wheelchair. Due to breathing problems, some boys may need to have a tracheostomy tube surgically placed in their trachea (windpipe), and some may need a respirator. Even with the best medical care, young men with Duchenne MD usually do not survive beyond their early thirties due to the life-threatening heart and breathing problems that develop due to the disease.

Sources:

"Duchenne Muscular Dystrophy (DMD)." Diseases. July 2007. Muscular Dystrophy Association. 1 Oct 2008

"NINDS Muscular Dystrophy Information Page." Disorders. 15 Sep 2008. National Institute for Neurological Disorders and Stroke. 1 Oct 2008

"About Duchenne." Understanding Duchenne. Parent Project Muscular Dystrophy. 1 Oct 2008

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