Condition: Duchenne muscular dystrophy (DMD) and its rarer and less severe form, Becker muscular dystrophy (BMD), are medical conditions caused by abnormal genes that cause progressive muscle weakness.
Background: DMD generally appears before age six; BMD usually does not appear until age eight or later. DMD occurs in one out of 3,500 male births; BMD occurs in three to six of every 100,000 male births. Both conditions primarily affect the skeletal muscles, as well as the heart. With DMD, muscle weakness worsens more rapidly; by adolescence, patients usually require a wheelchair. BMD is milder and worsens more slowly. Currently, there is no cure for either DMD or BMD.
Risk Factors: DMD and BMD affects boys whose mothers are carriers of the gene, or those children who have a spontaneous genetic mutation.
History and Symptoms: Lower limb weakness results in issues walking, standing or sitting. As it progresses, it can also cause cardiomyopathy, a heart disease that can cause irregular heartbeat, fatigue, shortness of breath and swelling in the legs and feet. Muscle contractures and scoliosis, an abnormal curvature of the spine, are also commonly seen. Patients can see a decline in pulmonary function as the muscles that control the lungs while breathing weaken.
Physical Exam: Initially, a patient’s weakness may be subtle. Neck and hip muscles may be weak. Patients may have thick calves and walk on their toes. The doctor will check for the Gower sign. Patients with DMD or BMD display this sign, where they move from lying on the floor to standing by “walking” their hands up their thighs, since they do not have sufficient muscle strength in their thighs alone to perform this movement.
Diagnostic Process: The rehab physician/PM&R physician may order a blood test to check for elevated levels of creatine phosphokinase (CPK), a muscle enzyme which when significantly elevated can indicate DMD or BMD. Genetic testing may also demonstrate the specific genetic abnormality that has led to DMD or BMD.
Rehab Management: Early rehabilitation should focus on maintaining strength and range of motion. However, muscle tissue can be damaged, so exercise should not be intense. In younger children, swimming or biking can be good activities. Oral corticosteroids have been used in DMD to slow its progression, keep kids on their feet for longer periods of time, and reduce scoliosis progression. Medicines to preserve heart function can also be used. Bracing of the ankles and splints can help with stability and help maintain joint range of motion. As the children age and the disease progresses, it is important to accommodate their needs to keep them as active and functional as possible. This can include power wheelchairs to make patients ambulatory as well as assistive technology to help with communication and community access. Discussions with the patient and family in regards to medical technology (to include tracheostomies and ventilators for breathing, and pacemakers and defibrillators to assist heart function) can also be important.
Other Resources for Patients and Families: The National Institutes of Health offers a listing of resources for patients with Duchenne or Becker muscular dystrophy and their families.