Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle.
There are many different kinds of muscular dystrophy. Symptoms of the most common variety begin in childhood, primarily in boys. Other types don't surface until adulthood.
Some people who have muscular dystrophy will eventually lose the ability to walk. Some may have trouble breathing or swallowing.
There is no cure for muscular dystrophy. But medications and therapy can help manage symptoms and slow the course of the disease.
The main sign of muscular dystrophy is progressive muscle weakness. Specific signs and symptoms begin at different ages and in different muscle groups, depending on the type of muscular dystrophy.
Duchenne muscular dystrophy
About half of people with muscular dystrophy have this variety. Although girls can be carriers and mildly affected, the disease typically affects boys.
About one-third of boys with Duchenne muscular dystrophy don't have a family history of the disease, possibly because the gene involved may be subject to sudden abnormal change (spontaneous mutation).
Signs and symptoms typically appear between the ages of 2 and 3, and may include:
Difficulty getting up from a lying or sitting position
Trouble running and jumping
Walking on the toes
Large calf muscles
Muscle pain and stiffness
Becker muscular dystrophy
Signs and symptoms are similar to those of Duchenne muscular dystrophy, but typically are milder and progress more slowly. Symptoms generally begin in the teens but may not occur until the mid-20s or even later.
Other types of muscular dystrophy
Some types of muscular dystrophy are defined by a specific feature or by where in the body symptoms first begin. Examples include:
Myotonic. Also known as Steinert's disease, this form is characterized by an inability to relax muscles at will following contractions. Myotonic muscular dystrophy is the most common form of adult-onset muscular dystrophy. Facial and neck muscles are usually the first to be affected.
Facioscapulohumeral (FSHD). Muscle weakness typically begins in the face and shoulders. The shoulder blades might stick out like wings when a person with FSHD raises his or her arms. Onset usually occurs in the teenage years but may begin in childhood or as late as age 40.
Congenital. This type affects boys and girls and is apparent at birth or before age 2. Some forms progress slowly and cause only mild disability, while others progress rapidly and cause severe impairment.
Limb-girdle. Hip and shoulder muscles are usually the first affected. People with this type of muscular dystrophy may have difficulty lifting the front part of the foot and so may trip frequently. Onset usually begins in childhood or the teenage years.
When to see a doctor
Seek medical advice if you notice signs of muscle weakness — such as increased clumsiness and falling — in yourself or your child.
Certain genes are involved in making proteins that protect muscle fibers from damage. Muscular dystrophy occurs when one of these genes is defective.
Each form of muscular dystrophy is caused by a genetic mutation particular to that type of the disease. Many of these mutations are inherited. But some occur spontaneously in the mother's egg or the developing embryo and can be passed on to the next generation.
Muscular dystrophy occurs in both sexes and in all ages and races. However, the most common variety, Duchenne, usually occurs in young boys. People with a family history of muscular dystrophy are at higher risk of developing the disease or passing it on to their children.
The complications of progressive muscle weakness include:
Inability to walk. Some people with muscular dystrophy eventually need to use a wheelchair.
Shortening of muscles or tendons around joints (contractures). Contractures can further limit mobility.
Breathing problems. Progressive weakness can affect the muscles associated with breathing. People with muscular dystrophy may eventually need to use a breathing assistance device (ventilator), initially at night but possibly also in the day.
Curved spine (scoliosis). Weakened muscles may be unable to hold the spine straight.
Heart problems. Muscular dystrophy can reduce the efficiency of the heart muscle.
Swallowing problems. If the muscles involved with swallowing are affected, nutritional problems and aspiration pneumonia may develop. Feeding tubes may be an option.
Your doctor is likely to start with a medical history and physical examination.
After that, your doctor may recommend:
Enzyme tests. Damaged muscles release enzymes, such as creatine kinase (CK), into your blood. In a person who hasn't had a traumatic injury, high blood levels of CK suggest a muscle disease — such as muscular dystrophy.
Electromyography. An electrode needle is inserted into the muscle to be tested. Electrical activity is measured as you relax and as you gently tighten the muscle. Changes in the pattern of electrical activity can confirm a muscle disease.
Genetic testing. Blood samples can be examined for mutations in some of the genes that cause different types of muscular dystrophy.
Muscle biopsy. A small piece of muscle can be removed through an incision or with a hollow needle. Analysis (biopsy) of the tissue sample can distinguish muscular dystrophies from other muscle diseases.
Heart-monitoring tests (electrocardiography and echocardiogram). These tests are used to check heart function, especially in people diagnosed with myotonic muscular dystrophy.
Lung-monitoring tests. These tests are used to check lung function.
There's no cure for any form of muscular dystrophy. But treatment can help prevent or reduce problems in the joints and spine to allow people with muscular dystrophy to remain mobile as long as possible. Treatment options include medications, physical therapy, and surgical and other procedures.
Your doctor may recommend:
Corticosteroids, such as prednisone, which can help improve muscle strength and delay the progression of certain types of muscular dystrophy. But prolonged use of these types of drugs can cause weight gain and weaken bones, increasing fracture risk.
Heart medications, such as angiotensin-converting enzyme (ACE) inhibitors or beta blockers, if muscular dystrophy damages the heart.
Several types of therapy and assistive devices can improve quality and sometimes length of life in people who have muscular dystrophy. Examples include:
Range-of-motion and stretching exercises. Muscular dystrophy can restrict the flexibility and mobility of joints. Limbs often draw inward and become fixed in that position. Range-of-motion exercises can help to keep joints as flexible as possible.
Exercise. Low-impact aerobic exercise, such as walking and swimming, can help maintain strength, mobility and general health. Some types of strengthening exercises also might be helpful. But it's important to talk to your doctor first because some types of exercise might be harmful.
Braces. Braces can help keep muscles and tendons stretched and flexible, slowing the progression of contractures. Braces can also aid mobility by providing support for weakened muscles.
Mobility aids. Canes, walkers and wheelchairs can help maintain mobility and independence.
Breathing assistance. As respiratory muscles weaken, a sleep apnea device may help improve oxygen delivery during the night. Some people with severe muscular dystrophy may need to use a machine that forces air in and out of their lungs (ventilator).
Surgery may be needed to correct a spinal curvature that could eventually make breathing more difficult.
Respiratory infections may become a problem in later stages of muscular dystrophy. It's important to be vaccinated for pneumonia and to keep up to date with influenza shots.
Dietary changes haven't been shown to slow the progression of muscular dystrophy. But proper nutrition is essential because limited mobility can contribute to obesity, dehydration and constipation. A high-fiber, high-protein, low-calorie diet may help.