MUSCULAR DYSTROPHY

What is it?

The term "muscular dystrophy" actually refers to a group of degenerative muscle diseases characterized by gradual weakening and deterioration of skeletal muscles, and sometimes the heart and respiratory muscles. Children with the disease are born with an abnormal genetic trait that causes their muscles to develop improperly.

The most common types of muscular dystrophy result in dramatic physical weakness, so children lose the ability to do things like walk, sit upright, breathe easily, and move their arms and hands. The increasing weakness often leads to other serious complications and, for many, a shortened life span. Other forms can result in relatively minor physical disabilities or develop late in life, allowing affected people to have fairly normal life spans and activity levels.

Who gets it?

In most cases, the genetic abnormality for muscular dystrophy is inherited, so the condition tends to run in families.

Some types of muscular dystrophy, including Duchenne, are X-linked, which means that the abnormality is carried on the X chromosome that the mother contributes. A girl receives two X chromosomes, one from each parent, while a boy receives a Y chromosome from the father and an X from the mother. As a result, it is almost always boys who develop symptoms; girls inherit a normal X chromosome that may "cancel out" the abnormal one.

Girls who carry the abnormal gene have a 50% chance of passing the condition to their sons.

What are the symptoms?

The symptoms of Duchenne usually appear between the ages of two and five. Parents may notice that their child stumbles more frequently, waddles, has difficulty going up stairs, and toe-walks. Toddlers may develop a swayed back to compensate for weakening hip-area muscles. Children may struggle to get up from a sitting position. Many children also develop enlarged calf muscles, a condition called calf pseudohypertrophy, as muscle tissue is destroyed and replaced by non-muscle tissue.

Symptoms can first appear during early childhood or late adult life, depending on the type of muscular dystrophy a child develops. For example, the symptoms of Becker dystrophy are similar to Duchenne, but they may start during the school-age years, are less severe, and allow children to live well into adulthood. In contrast, Duchenne dystrophy begins during early childhood and causes fairly rapid weakness.

What tests will the Doctor want to do?

In addition to a clinical history and a physical exam, we perform a test that measures blood levels of serum creatine kinase, a muscle enzyme that's released into the bloodstream when muscle fibers are deteriorating in the body; elevated levels indicate that something is causing muscle damage.

If a child is found to have a high level of this enzyme, the next test may be a DNA test or a muscle biopsy. The DNA test is used to check for gene abnormalities, while the muscle biopsy is used to examine a muscle tissue sample for patterns of muscle deterioration and abnormal levels of dystrophin, a building block of muscle. These tests reveal the type of muscular dystrophy the child has.

What is the treatment?

Muscular dystrophy is a treatable but not curable disease. These treatments improve muscle and joint function, slow muscle deterioration, and keep kids comfortable, active, and independent for a longer period of time.

Many children with muscular dystrophy also develop weakened heart and respiratory muscles. Because children can't cough out phlegm due to weakened respiratory muscles, they sometimes develop respiratory infections that can quickly become serious. Good general health care and regular vaccinations are especially important for children with muscular dystrophy to prevent these infections.

Many children eventually need devices to help them do simple things because they become so weak. Assistive technology devices can be customized to meet the changing needs of children, making them much more independent, comfortable, and active.