Muscular dystrophy (MD) is a group of so-called “X-linked” genetic disorders that causes progressive muscle weakness and degeneration of the skeletal muscles controlling movement. According to the National Institutes of Health, some forms of MD become apparent in infancy or early childhood while others don’t appear until middle age or later.
Who Is at Risk for Muscular Dystrophy
Being X-linked, muscular dystrophy almost exclusively affects males, with many boys inheriting the mutation from their mother.
In about one-third of children with muscular dystrophy, their mother is not a carrier for MD and they developed it as a new mutation.
About 1 in every 3,500 to 5000 boys are born with MD, with some 400 to 600 new cases each year in the United States.
The Most Common Types of MD
Duchenne MD is the most common form of muscular dystrophy, and is caused by the absence of the protein dystrophin. This is a devastating disorder that progresses rapidly, with most sufferers (who are almost all boys) unable to walk by age 12 and needing a respirator to breathe.
Becker MD is similar to but less severe than Duchenne MD. Facioscapulohumeral MD usually begins in the teenage years and causes progressive weakness in muscles of the face, arms, legs, and around the shoulders and chest. It progresses more slowly than Duchenne’s and symptoms range from mild to disabling.
The most common adult form of the disorder is Myotonic MD.
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Its symptoms include muscle spasms, cataracts, and endocrine and cardiac abnormalities.
According to the Centers for Disease Control, “there are a few treatments that can help slow the progression of muscle loss, such as use of steroids, but there is no cure.”
Symptoms of Muscular Dystrophy in Toddlers
Signs of Duchenne MD first begin to show when a child is between the ages of 3 and 6 years old and they notice that their child is having problems with motor skills.
The child may be falling down frequently, have difficulty getting up when he is sitting or lying down, or have difficulty climbing stairs. Children may walk with shoulders pushed back or on their toes in a kind of waddle, or may be delayed walking on their own. Parents may also notice the child has enlarged calf muscles, due to pseudohypertrophy. Getting tired easily during routine physical activity is another symptom of MD.
Testing for Muscular Dystrophy with CK Levels
If your pediatrician suspects that your child may have muscular dystrophy, they will likely begin by testing the creatine kinase (CK) level in your child’s blood. This muscle enzyme is very high in children with muscular dystrophy.
If your doctor discovers a high CK level, they will likely do DNA testing to look for mutations in the gene that makes dystrophin. If this genetic testing is negative, then a muscle biopsy may be done to confirm the diagnosis of muscular dystrophy.
Newborn Screening for Muscular Dystrophy
Although it is possible to screen newborns for muscular dystrophy by testing their level of creatine kinase, it is not routinely done.
One of the big problems is that only about 10 percent of newborns with a high CK level will actually have muscular dystrophy. The other 90 percent will have CK levels that return to normal when they are a few weeks old.
Muscular Dystrophy Treatments
The NIH reports that “the prognosis of MD varies according to the type of MD and the progression of the disorder.” Some cases may be mild and progress very slowly over a normal lifespan, while other cases may have more marked progression of muscle weakness, functional disability, and loss of the ability to walk. If your child had an MD diagnosis, you can learn more about your child’s case as you build your team of trusted healthcare professionals.
“Duchenne/Becker Treatment and Care.” Centers for Disease Control (2016).
“Muscular Dystrophy Information Page.” National Institutes of Health (2016).