Muscular Dystrophy

Muscular dystrophy is actually a group of congenital disorders characterized by progressive symmetrical wasting of skeletal muscles without neural or sensory defects. Paradoxically, these wasted muscles tend to enlarge because of connective tissue and fat deposits, giving an erroneous impression of muscle strength. Muscular dystrophy causes the muscles in the body to become very weak. The muscles break down and are replaced with fatty deposits over time.

Other health problems commonly associated with muscular dystrophy include the following:

• heart problems
• scoliosis - a lateral, or sideways, curvature and rotation of the back bones (vertebrae), giving the appearance that the person is leaning to one side.
• obesity

The most common form of muscular dystrophy is called Duchenne muscular dystrophy (DMD). Duchenne muscular dystrophy usually affects only males. It occurs in one out of 3,000 live male births. Muscular dystrophy rarely affects girls, but when it does, the condition is normally not as severe.

Causes

The muscular dystrophies are caused by genetic defects, which means they are inherited at birth. While the affected genes have been identified for some forms of muscular dystrophy, such as DMD, BMD, CMD, and most forms of LGMD, the genes responsible for the other forms have not yet been identified.

Signs and symptoms

Although the four types of muscular dystrophy cause progressive muscular deterioration, the degree of severity and the age of onset vary.

Duchenne's muscular dystrophy - Duchenne's muscular dystrophy begins insidiously, between the age of 3 and 5. It affects leg and pelvic muscles initially but eventually spreads to the involuntary muscles. Muscle weakness produces a waddling gait, toe-walking, and lordosis.

Children with this disorder have difficulty climbing stairs, fall down often, can't run properly, and their scapulae flare out (or "wing") when they raise their arms. Calf muscles especially become enlarged and firm. Muscle deterioration progresses rapidly, and contractures develop. Usually, these children are confined to wheelchairs by ages 9 to 12.

Late in the disease, progressive weakening of cardiac muscle causes tachycardia, electrocardiogram abnormalities, and pulmonary complications. Death commonly results from sudden heart failure, respiratory failure, or infection.

Becker's muscular dystrophy - Symptoms are similar to DMD, but usually milder. Patients with BMD often can walk independently into their twenties or early thirties because the same pattern of leg weakness, unsteadiness, and permanent muscle tightening (contractures) occurs later with BMD. Symptoms may also include mild and slowly progressing scoliosis, heart muscle disease (cardiomyopathy), irregular heartbeats (arrhythmias), congestive heart failure, fatigue, shortness of breath, chest pain, and dizziness. Eventually, patients may need a ventilator to help with breathing because of respiratory weakness.

Facioscapulohumeral dystrophy - fa -she-o- skap -you-lo- hyoo -meh-rul) muscular dystrophy (FSHD) can affect both guys and girls, and it usually begins during the teens or early adulthood. FSHD affects muscles in the face and shoulders and sometimes causes weakness in the lower legs. People with this type of MD might have trouble raising their arms, whistling, or tightly closing their eyes. How much a person with this form of muscular dystrophy is affected by the condition varies from person to person. It can be quite mild in some people.

Early symptoms include inability to pucker the mouth or whistle, abnormal facial movements, and absence of facial movements when laughing or crying. Other signs consist of diffuse facial flattening that leads to a masklike expression, winging ofthe scapulae, inability to raise the arms above the head, and, in infants, inability to suckle.

Limb-girdle dystrophy - Muscles usually affected first by this form of muscular dystrophy include:

• Hips
• Shoulders

This form then progresses to the arms and legs, though progression is slow. Limb-girdle MD may begin from early childhood to adulthood.

Distal muscular dystrophy - This group involves the muscles farthest away from the center of the body - those of the hands, forearms, feet and lower legs. The severity is generally less than for other forms of MD, and this form tends to progress slowly. Distal MD generally begins in adulthood between the ages of 40 and 60.

Congenital muscular dystrophy (CMD) is the term for all types of MD that show signs in babies and young children, although the MD isn't always diagnosed right away. Like other forms of MD, CMD involves muscle weakness and poor muscle tone. Occurring in both girls and boys, it can have different symptoms. It varies in how severely it affects people and how quickly or slowly it worsens. In rare cases, CMD can cause learning disabilities or mental retardation.

Diagnosis

Typical clinical findings, family history, and test findings are used to diagnose the disease. If another family member has muscular dystrophy, its clinical characteristics can indicate the type of dystrophy the patient has and how he may be affected.

Electromyography typically demonstrates short, weak bursts of electrical activity in affected muscles. A muscle biopsy shows variations in the size of muscle fibers and, in later stages, fat and connective tissue deposits. In Duchenne's muscle dystrophy, a muscle biopsy reveals an absence of dystrophin.

Immunologic and molecular biological techniques now available in specialized medical centers facilitate accurate prenatal and postnatal diagnosis of Duchenne's and Becker's muscular dystrophies. These techniques also help to identify a person as a carrier.

In addition, these newer techniques are replacing muscle biopsy and serum creatine kinase tests as diagnostic procedures.

Treatment

To date, scientists have found no treatment that can stop the progressive muscle impairment of muscular dystrophy. However, orthopedic appliances as well as exercise, physical therapy, and surgery to correct contractures can help preserve the patient's mobility and independence.

Family members who are carriers of muscular dystrophy should receive genetic counseling regarding the risk of transmitting this disease.

Self-care tips

There is currently no way to prevent muscular dystrophy if you have inherited the genes responsible for these disorders. However, accurate genetic tests are now available for the muscular dystrophies for which the mutated gene has been identified. These can be useful for family planning purposes for those with a family history of this disease. If you have been diagnosed with a form of muscular dystrophy, good nutrition is an important part of your general health.