Muscular Dystrophy

What Is Muscular Dystrophy?

Muscular dystrophy (MD) is a group of inherited diseases in which the muscles that control movement (called voluntary muscles) progressively weaken. In some forms of this disease, the heart and other organs are also affected.

There are nine major forms of muscular dystrophy:

• Myotonic
• Duchenne
• Becker
• Limb- girdle
• Facioscapulohumeral
• Congenital
• Oculopharyngeal
• Distal
• Emery-Dreifuss

Muscular dystrophy can appear in infancy up to middle age or later, and its form and severity are determined in part by the age at which it occurs. Some types of muscular dystrophy typicallyaffect only males; some people with MD enjoy a normal life span with mild symptoms that progress very slowly; others experience swift and severe muscle weakness and wasting, dying in their late teens to early 20s.

The various types of MD affect more than 50,000 Americans. Through advances in medical care, children with muscular dystrophy are living longer than ever before.

Muscular Dystrophy Causes and Risk Factors

Muscular dystrophy is caused by defects in certain genes, with type determined by the abnormal gene. In 1986, researchers discovered the gene that, when defective or flawed, causes Duchenne muscular dystrophy. In 1987, the muscle protein associated with this gene was named dystrophin. Duchenne muscular dystrophy occurs when that gene fails to make dystrophin. Becker muscular dystrophy occurs when a different mutation in the same gene results in some dystrophin, but it's either not enough or it's poor in quality. Scientists have discovered and continue to search for the genetic defects that cause other forms of muscular dystrophy.

Most of the muscular dystrophies are a form of inherited disease called X-linked disorders or genetic diseases that mothers can transmit to their sons even though the mothers themselves are unaffected by the disease.

Men carry one X chromosome and one Y chromosome. Females carry two X chromosomes. Thus, in order for a girl to become affected by muscular dystrophy, both their X chromosomes would have to carry the defective gene -- an extremely rare occurrence, since their mother would have to be a carrier (one defective X chromosome) and their father would have to have muscular dystrophy (since men carry just one X chromosome, the other is a Y chromosome).

A female who carries the defective X chromosome can pass the disease to their son (whose other chromosome is a Y, from the father).

A few muscular dystrophies aren't inherited at all and occur because of a new gene abnormality or mutation.

Muscular Dystrophy Diagnosis

To start, your doctor will examine your child and ask questions about medical and family health history. Muscular dystrophy is diagnosed using several different tests. These may include:

Muscle biopsy. A small piece of muscle tissue is removed and examined to confirm the diagnosis or rule out another muscle disease.

Genetic (DNA) testing. Genes passed down through families can cause some forms of muscular dystrophy. A blood test can determine if you or your child has the gene.

Neurological tests. Various tests are done to check nervous system function, reflexes, and coordination. One example is a nerve conduction study, also called a nerve function test, or electromyography (EMG).

Enzyme tests. These are blood tests that check for proteins, or enzymes, linked to muscle weakness. People with muscular dystrophy have high levels of the enzyme creatine kinase. It’s made when muscles are damaged. They also have higher levels of serum aldolase, which is made when your body breaks down sugar into energy.

Heart monitoring. An electrocardiogram may be done to check for an abnormal heartbeat. Some types of muscular dystrophy cause irregular heartbeats.

MRI or ultrasound. These imaging tests give the doctor a look at muscle quality and can reveal if fat is replacing muscle tissue.

Muscular Dystrophy Treatment

There is no cure for muscular dystrophy, but treatments can help manage symptoms and improve quality of life.

Medications

Prescription drugs are available to control muscular dystrophy symptoms or slow their progression. Medications for muscular dystrophy include:

• Steroids. Corticosteroids, such as prednisone and deflazacort (Emflaza), are the standard of care for muscular dystrophy. They help improve muscle strength and breathing and decrease weakness. Side effects include high blood pressure and weight gain. People who use steroids for a long time are at risk for brittle bones.
• Medicines targeting gene mutations. Eteplirsen (Exondys 51) and golodirsen (Vyondys 53) increase the level of the gene dystrophin. They’re approved to specifically treat Duchenne muscular dystrophy.
• Anticonvulsants. Often used to treat epilepsy, these antiseizure drugs may also help reduce muscle spasms.
• Immunosuppressants. These powerful medicines are often used to treat lupus and other autoimmune diseases. When given to people with muscular dystrophy, they may help prevent some muscle cell damage.
• Antibiotics. The doctor may prescribe an antibiotic to treat a lung infection, which is common in people with muscular dystrophy.

Physical therapy

Physical therapy helps keep joints and muscles flexible. It’s an important part of a muscular dystrophy treatment plan.

The goal of physical therapy is to improve strength in the large muscle groups and prevent scoliosis and contractures.

Physical therapy for muscular dystrophy may involve:

• Range of motion exercises
• Stretching
• Low-impact workouts, such as swimming or water exercise (aquatic therapy)

Respiratory care

Muscle weakness can affect the lungs, making breathing difficult. A respiratory therapist can teach you and your child how to properly use a mask, nose device, or mouthpiece.

Mobility and positioning aids

Braces, walkers, or wheelchairs help provide mobility and independence to people with muscular dystrophy. Standing with a walker, even for just a little bit each day, boosts blood flow and helps build better bones.

Speech therapy

Muscle weakness in the face and throat can make speaking difficult. Learning how to properly pace breathing and talking can be helpful. A speech therapist can also show you how to use speech communication devices.

Surgery

Surgery may be recommended to manage or correct complications of muscular dystrophy. For example, cataract surgery may be done to replace a cloudy eye lens. Or a person with muscular dystrophy may need spinal fusion surgery to treat scoliosis, or heart surgery to implant a pacemaker.

Muscular Dystrophy Complications

The complications of muscular dystrophy depend on the type. Some types are mild, while others are serious and get worse very fast. Worsening muscle weakness can affect the ability to walk, breathe, swallow, and speak.

Complications of muscular dystrophy can include:

Breathing problems. Progressive weakness in the breathing muscles (diaphragm) makes it hard to take a breath. That raises the risk for lung infections such as pneumonia.

Curving of the spine (scoliosis). Weakness in the muscles supporting the backbone causes the spine to become curved. Most people with Duchenne muscular dystrophy need scoliosis surgery.

Heart problems. Some types of muscular dystrophy cause abnormal and dangerous changes in the heartbeat. You need a pacemaker to regulate it. Muscular dystrophy can also cause the heart muscle to become weak (cardiomyopathy). That leads to heart failure.

Swallowing difficulty. Weakness affects the muscles in the esophagus, and causes problems with chewing and swallowing. This can lead to choking. Some people with muscular dystrophy will need a feeding tube.

Shortening of the tendons or muscles around the joints (contractures). Bracing and tendon release surgery can help prevent some contractures.

Vision problems. Some types of muscular dystrophy cause clouding of the eye lens (cataracts).

Need for a wheelchair. Weakness in the large muscles of the legs makes it difficult to walk, stand, kneel, or climb. Some people with muscular dystrophy eventually need to use a wheelchair.

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