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Muscular dystrophy (MD) is a group of rare diseases that cause muscles to weaken and deteriorate. MD affects the voluntary muscles that control movement in the arms, legs, and trunk. It also can affect involuntary muscles, such as the heart and respiratory muscles.
MD is a progressive disease, meaning that it worsens over time. Depending upon the form of MD, children and adults may gradually lose the ability to walk and do other everyday activities. In later stages of some forms of the disease, heart and breathing problems may develop.
Although there is currently no cure for MD, there are medications that may slow the rate of muscle degeneration, as well as other treatment options to improve function and assist in activities of daily living.
Muscular dystrophy is a genetic disorder. It is caused by defects in the genes that produce proteins that are necessary for healthy muscle development and function.
In most cases, MD is inherited — it passes from parent to child. A few incidences of MD, however, may occur due to a new genetic abnormality. This is called spontaneous mutation.
There are nine major types of MD affecting people of all ages, from infancy to middle age or later. These forms of MD differ in terms of age of onset and muscles affected. How severe the symptoms are and how rapidly the disease progresses also varies.
The two most common types of MD that affect children are Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD).
Both DMD and BMD affect boys almost exclusively. They are sex-linked (X-linked) disorders that typically pass from a mother (who has no symptoms) to her son. Girls are rarely affected.
Both Duchenne MD and Becker MD cause weak muscles, lack of coordination, and progressive disability.
Duchenne Muscular Dystrophy (DMD)
Duchenne MD begins with muscle loss in the pelvis, upper arms, and legs. The first signs and symptoms of DMD develop between ages 2 to 5 years. Symptoms include:
- Difficulty walking, such as lateness in learning how to walk (older than 18 months), having a waddling gait, or walking on the toes or balls of the feet
- Difficulty running or jumping because of weakness in leg muscles
- Frequent falls, stumbling, and difficulty climbing stairs
- Difficulty standing from a lying or sitting position
- Reduced endurance
- Enlarged calf muscles
- Mild mental developmental delay (in some patients)
Many children with DMD lose their ability to walk by late childhood and require wheelchairs. As muscles continue to weaken in the back and chest, most children develop curvature of the spine (scoliosis). By adolescence, DMD usually progresses to weaken the heart and respiratory muscles.
Becker Muscular Dystrophy (BMD)
Becker MD begins with muscle loss in the hips, pelvis, thighs and shoulders. BMD is basically a milder form of Duchenne MD. Symptoms include:
- Physical difficulties similar to Duchenne muscular dystrophy
- Waddling gait, perhaps walking on toes or sticking out the abdomen to balance weak muscles
BMD progresses more slowly over the course of decades, and is a milder and less predictable disease. Some men with BMD need wheelchairs by age 30 years or later; others manage for many years with minor aids, such as a walking cane.
If you think your child may have any form of MD, see your doctor as soon as possible for diagnosis and comprehensive care.
To diagnose MD, your doctor will take a complete medical history of your child and the family. Your doctor will also perform a thorough physical examination of your child and may use laboratory tests to confirm the diagnosis of MD.
Your doctor will discuss your child's general health and past illnesses. Be sure to provide your child's complete medical history, including any other health problems. Your doctor will also ask you to describe your child's symptoms. During the appointment, tell your doctor if other family members have any signs or symptoms of MD. Also, be prepared to discuss what age your child achieved growth milestones, such as learning how to walk.
Your doctor will want to see how your child stands up from a sitting position on the floor. Because of weak leg muscles, children with DMD stand up in a unique way that has been termed the Gower's maneuver. They start out on their hands and feet, planting their feet widely apart and pushing up their bottom first. Then they use their hands to push up on their knees and thighs.
Your doctor will also watch your child walk. He or she may carefully test your child's muscles and nervous system.
Your doctor may use certain laboratory tests to confirm that your child has MD, or to monitor for changes caused by the disease
- Blood tests. Your doctor checks a blood sample for high levels of the enzyme creatine kinase, which can indicate muscle damage.
- Electromyography. Your doctor puts small electrodes into muscle to measure electrical activity. Changes in the pattern of activity can show disease.
- Muscle biopsy. Your doctor removes a small piece of muscle to study in the laboratory. This can distinguish various forms of MD from other muscle diseases.
- Genetic testing. Sometimes, your doctor can study a blood sample to identify an abnormal gene and diagnose MD.
- Bone mineral density. The bones of children can become weak over time, especially for children in wheelchairs. Your doctor might test bone density to determine if treatment is needed.
- Pulmonary function test. Your doctor may also monitor for changes in respiratory (breathing) function over time with a special breathing test.
Doctors do not yet have a cure for any type of MD. Fortunately, timely interventions can help slow progression of complications and maximize your child's quality of life.
The goals of nonsurgical treatment of MD include keeping your child's body flexible, upright, and mobile, and helping your child function independently for as long as possible.
Your doctor may recommend various nonsurgical treatments:
- Physical therapy and bracing to prevent contractures. Your doctor may prescribe daily stretching exercises to improve your child's ability to walk. Regular, moderate physical therapy may help maintain range of motion in stiff or "frozen" joints (contractures). Walking braces for the ankle-foot or the knee-ankle-foot can help support weak muscles and keep the body flexible, slowing progression of contractures.
- Medications. Your doctor may prescribe anti-inflammatory corticosteroid medications to improve muscle strength and delay progression of DMD. Although corticosteroids have been proven effective in slowing muscle degeneration, these medications can cause concerning side effects.
- Assistive devices. Rehabilitative devices such as canes, walkers, wheelchairs, strollers, and power wheelchairs can help maintain your child's mobility and independence.
Sometimes it helps to make modifications to your home, such as widening doorways and installing wheelchair ramps.
Eventually, as respiratory muscles weaken, your child may also need the assistance of a breathing device (ventilator).
Your doctor may recommend surgical procedures to help maintain your child's functional skills and improve quality of life.
- Surgical release of contractures. If contractures are severe, your doctor may recommend tendon release surgery. In this procedure, your surgeon lengthens the tendon to relieve the muscle tension. The tendon then heals at the longer length. Some surgeries can help the child continue to walk.
- Spinal fusion for scoliosis. The scoliosis curve in a wheelchair-dependent child with MD can become so severe that it aggravates breathing problems. Having spine surgery before this happens can help with breathing function, lessen back pain, and improve sitting balance. All of these factors improve the child's quality of life.
Your doctor may recommend surgery when the spinal curve reaches a certain size (greater than 20°-30°). During a spinal fusion procedure, the curved portion of the spine is put in a straighter position and "fused" together using bone graft. Metal rods are typically used to hold the spine in place while the bone graft fuses with the existing spinal bones.
Like all children, those with MD need to feel loved, valued, and safe. They need to develop strong self-esteem. Parents, siblings, other family members, and friends can help by seeing the child first, not the disease.
Keep a positive attitude, communicate openly and honestly, and be patient and optimistic. By giving your love, support, and encouragement, you can help your child have a happy and rewarding life, despite the challenges of MD. Some tips for coping:
- Encourage your child to stay independent for as long as possible.
- Answer your child's questions about MD. Give an older child more information about the disease, and allow him or her to take part in medical decision-making.
- Ask for and accept help from other people. Family members of people with MD face significant physical, emotional, and financial commitments.
- Do not blame yourself for your child's MD. At various times, everyone in the family may experience all the stages of grief—denial, anger, bargaining, depression and acceptance. As MD progresses, crisis points can trigger powerful emotions. Consider joining a support group to learn coping strategies and to know that you are not alone.
Reviewed by members of POSNA (Pediatric Orthopaedic Society of North America)
The American Academy of Orthopaedic Surgeons
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