Duchenne and Becker Muscular Dystrophy

The Questions and Answers that follow aim to provide an introduction to Duchenne and Becker muscular dystrophy (DMD) for parents and other family members. Following those, we offer links to selected resources for more information and support and a list of valuable services.

More information about many topics relevant to children with DMD and many other chronic conditions and their families can be found in the left menu. Detailed information aimed at primary care doctors can be found in our Duchenne and Becker Muscular Dystrophy module.

Duchenne muscular dystrophy (DMD) is a progressive form of muscular dystrophy that occurs primarily in boys. It is caused by an alteration (mutation) in a gene, called the DMD gene that can be inherited in families, however DMD often occurs in people from families without a known family history of the condition. In individuals who have DMD, muscle fibers break down and are replaced by fibrous and/or fatty tissue causing the muscle to gradually weaken leading to progressive loss of muscle function, which begins in the lower limbs.

DMD is inherited in an X-linked recessive pattern. Males have only one copy of the X chromosome from their mother and one copy of the Y chromosome from their father. If their X chromosome has a DMD gene mutation, they will have Duchenne muscular dystrophy. Females, on the other hand, have two copies of the X chromosomes. Since females have two copies of this gene, if one copy does not work, they have a second back-up copy to produce the dystrophin protein. A woman who has a genetic change in one of her two copies is said to be "a carrier" of Duchenne muscular dystrophy. Carriers do not have Duchenne muscular dystrophy and most are unaware that they even carry this change in their genetic material unless they have a family history of DMD.

The symptoms usually appear before age 6 and may appear as early as infancy. Motor milestones, such as the age the child first walks, may be delayed.Boys may have a waddling gait and difficulty climbing stairs. Calf muscles are usually noted to be enlarged. There is a steady decline in muscle strength between the ages of 6 and 11 years; treatment with steroids helps to alleviate some of this progression. Scoliosis, a curvature of the spine may appear. Muscular weakness and skeletal deformities frequently contribute to breathing disorders. Cardiomyopathy (enlarged heart) may begin in the early teens in some, and in all after the age of 18 years. Few individuals with DMD live beyond their 30s. Breathing complications and subsequent infection and cardiomyopathy are common causes of death.

Most boys with Duchenne muscular dystrophy are not diagnosed until they start displaying symptoms unless there is a family history of the condition. Sometimes a blood test may be done as a screening test for high levels of a protein called creatine kinase. Creatine kinase is normally found in muscle but when muscles are abnormal as in DMD, it leaks into the bloodstream. DMD is confirmed by genetic testing. Different types of genetic tests are able to provide specific and more detailed information about the DNA mutation. Genetic confirmation is crucial as it will assist in determining if your son qualifies for a number of clinical trials and will assist the family with decisions related to prenatal diagnosis and future pregnancies. Your doctor may also recommend a muscle biopsy which is the process of taking a small sample of muscle for analysis. Tests on the muscle biopsy can provide information on the amount of dystrophin protein present in the muscle cells.

Boys will show progressive weakness first manifest as difficulty climibing stairs, then walking, and finally they will need a wheelchair for all mobility. Upper limb function and maintenance of good posture is increasingly difficult and complications such as scoliosis and heart problems may occur. The condition shortens life expectancy but with high standards of medical care young men with Duchenne muscular dystrophy are often living well into their 30s. Some boys with Duchenne muscular dystrophy will also develop learning and or behavioral difficulties. Early treatment with steroids may help prolong life and ability to walk. News about positive clinical trial data has just been released that may help boys with certain gene mutations with Duchenne muscular dystrophy.

As DMD is an X-linked recessive condition, the chance of passing on the gene mutation from a mom known to be a carrier of DMD to a child is different for males and females. Females who carry the changed copy of the gene have a 50 percent chance of passing it on with each pregnancy. Thus, there is a 25 percent chance of having a affected child with DMD; 50 percent of boys have the chance of having DMD and 50 percent of girls will be carriers). The chance of a woman who has one affected son (and no family history) of being a carrier of the changed DMD gene is approximately 2/3. For more information, talk to your neurologist, geneticist, or genetic counselor, and see the Medical Home Portal for more information. See Duchenne Muscular Dystrophy: Genetics.

The medication prednisone, a type of steroid, is given to improve the strength and function of individuals with DMD, prolonging the ability to walk by 2 to 5 years. Possible side effects of prednisone include weight gain, high blood pressure, behavior changes, and delayed growth. Boys with DMD need to be monitored closely. A synthetic form of prednisone, Deflazacort, is used in Europe and believed to have fewer side effects than prednisone. Otherwise, treatment for Duchenne muscular dystrophy is aimed at the symptoms. For instance, management of dilated cardiomyopathy with anti-congestive medications is used and braces may help contratures that develop in the legs. A multidisciplinary approach, with the input of specialists in many different areas, is optimum in the management of boys with DMD. Guidelines for treatment are available. See DMD Guidelines (TreatNMD, thelancet.com).

Discussions around this issue will vary greatly between families and will depend on the age and cognitive level of the boy with DMD and family preferences. Often, discussions need to be held many times over the years as the boy gains understanding or hears new information. Sometimes, the boy with DMD understands a fair amount without being told; the first step therefore is to determine his level of understanding. An opportunity to attend MDA camp where the boy can meet other children with DMD and see boys in various stages is often helpful. Research on DMD is progressing quickly and discussions should hold out hope for the future. Information about communicating with a critically ill child may provide some general guidance in how to communicate about these issues. See Communicating Bad News to Children.

There are various types of external catheters, used primarily by men with spinal cord injuries. Although many providers worry about the risk of infection and skin irritation/breakdown with these systems, many users are quite satisfied. To find a provider familiar with the use and possible side effects, call a local rehabilitation facility, specifically one with expertise in spinal cord injury, and ask to set up an appointment with a provider who is familiar with them.