Duchenne muscular dystrophy is the most common fatal genetic disorder diagnosed in childhood, affecting approximately 1 in every 3,500 live male births (about 20,000 new cases each year). Because the Duchenne gene is found on the X-chromosome, it primarily affects boys; however, it occurs across all races and cultures.
Duchenne results in progressive loss of strength and is caused by a mutation in the gene that encodes for dystrophin. Because dystrophin is absent, the muscle cells are easily damaged. The progressive muscle weakness leads to serious medical problems, particularly issues relating to the heart and lungs. Young men with Duchenne typically live into their late twenties.
Duchenne can be passed from parent to child, but approximately 35% of cases occur because of a random spontaneous mutation. In other words, it can affect anyone. Although there are medical treatments that may help slow its progression, there is currently no cure for Duchenne.
If a boy has a combination of the traits listed below, he should be tested for Duchenne:
Unfortunately, once a child is born with Duchenne, its progression cannot be stopped. However, once there is a known case of Duchenne within a family, it is possible to offer prenatal diagnoses in future pregnancies (for both the mother of the diagnosed child and for other women in the family) through genetic testing.
Genetic testing refers to analysis of the gene itself, and it identifies the specific disease causing mutation. Genetic testing can also predict a person’s risk of developing a disease. For expectant mothers, genetic studies performed during pregnancy can detect Duchenne with about 95% accuracy. Doctors may make recommendations about childbearing options.
Before testing, families should understand:
Duchenne and Becker muscular dystrophies are not specific to any one group, crossing all cultures and races. What sets these two disorders apart from other muscular dystrophies is that they occur almost exclusively in young men, making them gender-linked disorders.
The dystrophin gene is carried on the X-chromosome. Young men have one each of the X- and Y-chromosomes, whereas girls have two X-chromosomes. Young men are therefore at greater risk of inheriting disorders caused by damaged genes on the X-chromosome, since they lack a second X-chromosome to “make up” for the damaged gene.
One of our largest known genes, dystrophin is an important muscle protein that acts as a kind of glue, holding muscles together by maintaining the structure of muscle cells.
Dystrophin is also believed to carry signals between the inside and outside of muscle fibers. Without dystrophin, muscles are unable to operate properly, and eventually suffer progressive damage.
The dystrophin gene is carried on the X-chromosome. Boys have only one X-chromosome, making them more susceptible to dystrophin damage, as they lack a second X-chromosome to make up for the damaged gene.
When a boy’s body is not able to produce any dystrophin at all, he is diagnosed with Duchenne. In Becker muscular dystrophy, a shortened form of dystrophin is generated.
Duchenne is usually passed from parent to child, but many cases are the result of random spontaneous genetic mutations, which can occur during any pregnancy. In fact, about one out of every three cases occurs in families with no previous history of Duchenne.
Newborn screening is able to detect Duchenne muscular dystrophy, but there are still many issues that need to be considered by the National Institutes of Health (NIH) before widespread newborn screening will be available.
Parents or teachers are often the first to notice the early signs of Duchenne, such as speech delay, enlarged calf muscles, and the inability to keep up with peers.
There are reliable tests to help doctors diagnose a boy with Duchenne. The following tests are typically used to confirm a preliminary diagnosis of Duchenne:
Boys with Duchenne may develop later than children of the same age—for example, speaking, sitting up, and walking. Cardiac problems eventually occur with Duchenne and may start early or during the teenage years.
Typically, boys with Duchenne lose their ability to walk between the ages of ten and fourteen. By their late teens, young men lose the strength in their upper bodies, including the ability to move their arms. Also during their teenage years, young men with Duchenne usually need help with breathing at night.
Over time, their breathing or respiratory systems weaken, and they require constant support. Young men with Duchenne typically survive into their twenties or early thirties.
While there’s currently no cure, with informed and timely treatment, boys with Duchenne can maintain their independence, walk, and live longer than ever before.
The rate of progression and severity of symptoms are different for each boy, but there are four stages usually associated with Duchenne.