Muscular dystrophy (MD) is an inherited (genetic) disorder of the muscles. It is called a neuromuscular disease. There are several types. Becker muscular dystrophy (BMD) is a rare type. It usually has milder symptoms and occurs later than Duchenne muscular dystrophy (DMD), which is more common. BMD causes weakness of skeletal muscles, breathing muscles, and the heart muscle. Over time, the muscle fibers break down. Although skeletal muscle involvement is generally less severe than in DMD, heart involvement is often more of a problem with BMD.
BMD is a genetic disease. This means it passes from parents to children. It is caused by a faulty gene on the X chromosome. It mostly affects boys. Girls are only carriers and usually don’t have symptoms.
People normally have 23 pairs of chromosomes in each cell of their body. One set of 23 chromosomes comes from the mother, and one set of 23 chromosomes comes from the father. Each chromosome contains many genes. One of these pairs of chromosomes controls a person’s sex. If this pair is two X chromosomes (XX), then the child is a female. If this pair is one X and one Y chromosome (XY), then the child is a male.
The faulty BMD gene is an X-linked recessive gene. This means the gene needs to be on each of her two X chromosomes for symptoms of the disease to occur in girls. She would need to inherit the faulty gene from both her mother and her father. If she has only one faulty gene on one X chromosome, she is a carrier of the disease but will likely not have symptoms. Boys have only one X chromosome, so if their X chromosome has a faulty gene, they will have symptoms.
Children are more at risk for BMD if they have a family member with the disease. Girls are rarely affected by this type of muscular dystrophy.
Symptoms usually start during the teen or early adult years. They can include:
Muscle cramping and feeling weak when exercising
Trouble walking, running, jumping, climbing stairs
Walking on tips of toes
Weakness in arms and shoulders
Difficulty breathing, especially with heart involvement
The symptoms of BMD can be like other health conditions. Make sure your child sees their healthcare provider for a diagnosis.
The healthcare provider will ask about your child’s symptoms and health history. They may also ask about your family’s health history to find out if other family members have had muscular dystrophy. They will give your child a physical exam. Your child may also have tests, such as:
Blood tests. These may include genetic blood tests. Some genetic tests can be done with saliva and don't need blood tests.
Electromyogram (EMG) and nerve conduction studies. These tests check if muscle weakness is a result of muscle or nerve damage.
Muscle biopsy. A small sample of muscle tissue is taken and looked at under a microscope.
Electrocardiogram (ECG). This is a test that records the electrical activity of the heart. It shows abnormal rhythms (arrhythmias) and detects heart muscle damage.
Echocardiogram. This is an ultrasound test of the heart muscle. It shows a picture of how strong the heart muscle is pumping.
Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.
There is no known cure for BMD or treatment to stop the muscles from weakening. The goal of treatment is to keep muscles as strong as possible to allow a child to function independently. Treatment almost always includes several kinds of specialists. It also includes testing over time, such as imaging, EMG, and heart and pulmonary studies.
Treatment choices include:
Physical therapy to strengthen muscle and help prevent muscle contractures
Braces and splints
The use of steroid medicines, though they can have unwanted side effects
Surgery to treat contractures
Medicines for heart disease, bone disease, and respiratory disease when they occur
Medicines from clinical research trials
Talk with your child’s healthcare providers about the risks, benefits, and possible side effects of all treatments.
Children with BMD may have additional health problems, such as:
Heart muscle weakening and not pumping blood well (dilated cardiomyopathy)
Breathing and lung problems
Scoliosis, a sideways curving of the back bones (vertebrae)
Diet, nutrition, and digestive problems
Trouble focusing, learning, or controlling emotions
Complications from anesthesia, for which special care is needed
Your healthcare provider may advise genetic counseling. You can discuss with a counselor the risk for BMD in a future pregnancy.
BMD is a condition that gets worse over time (progressive). It needs lifelong management. Walking and sitting often become more difficult as a child grows. In time, some will eventually need a wheelchair. This is because the leg muscles become too weak to work. Often, those with BMD can continue to walk for many years. In some cases, a child may need a wheelchair earlier.
Your child will also need a heart imaging test every 1 to 2 years. This may be a heart echocardiogram or MRI. These tests look at the function and health of the heart. A child with BMD will need special care during surgery to prevent problems from anesthesia.
People with BMD usually live until their 40s. Problems from cardiomyopathy are a common cause of death.
A healthcare team will work with your family to improve your child's function and give support as you learn to care for your child's needs.
You can contact the Muscular Dystrophy Association ( www.mda.org) for support, resources, and help.
Call the healthcare provider if your child has:
Symptoms that don’t get better or get worse
Becker muscular dystrophy (BMD) is a rare inherited disorder of the muscles.
BMD causes weakness of skeletal muscles, breathing muscles, and the heart muscle. Over time, the muscles may become too tight and pull together painfully.
Children are more at risk for BMD if they have a family member with the disease. Girls are rarely affected.
There is no known cure for BMD or treatment to stop the muscles from weakening. The goal of treatment is to keep muscles as strong as possible to allow a child to function independently.
Your healthcare provider may advise genetic counseling. You can discuss with a counselor the risk of BMD in a future pregnancy.
Tips to help you get the most from a visit to your child’s healthcare provider:
Know the reason for the visit and what you want to happen.
Before your visit, write down questions you want answered.
At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.
Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
Ask if your child’s condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if your child does not take the medicine or have the test or procedure.
If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your child’s provider after office hours, and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.