What Is Becker Muscular Dystrophy?

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Becker muscular dystrophy (BMD) is a type of muscular dystrophy, a genetic condition that causes progressive weakness and atrophy of the voluntary muscles of the body. BMD primarily affects males, and onset usually occurs in the teens or early 20s, but can occur later in life.

It is named after Peter Emil Becker, a German doctor who first noted this variant of Duchenne muscular dystrophy (DMD) in the 1950s after recognizing that symptoms of BMD are milder than those of DMD.

In BMD, muscle deterioration is much slower and more varied than in Duchenne muscular dystrophy, the most common type of muscular dystrophy.

Becker muscular dystrophy is caused by a gene abnormality that results in abnormal production of the dystrophin protein found in muscles. This protein helps muscles function, but in BMD, it is impaired, therefore causing a myriad of symptoms.

Boy with muscular dystrophy lays on a mat holding a blue bar as therapist stretches his left hamstring.

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Becker Muscular Dystrophy Symptoms

The muscles of the hips, pelvis, and thighs are usually the first muscles to be affected in BMD. This can cause a waddling gait, frequent falls, or difficulty running or jumping. The weakness of these muscles may also cause someone to walk on their toes with their stomach jutting out.

Muscle cramping and a decreased ability to exercise can also be some of the first signs of BMD. Muscle fibers in certain areas of the body (like the ankles) may shorten, causing contractures or the inability to move the joint around them.

In some cases, the heart muscle is also affected, causing symptoms such as difficulty breathing, fluid buildup around the lungs, and swelling in the legs or feet.

Other symptoms can include a loss of balance and coordination, as well as cognitive problems. However, unlike the muscle weakness that occurs in BMD, cognitive problems do not get worse over time.

Causes

Becker muscular dystrophy is caused by a mutation in the DMD gene on the X chromosome, which controls the production of the dystrophin protein that helps form muscle cells. Smaller versions (isoforms) of the protein are also produced in the brain.

Unlike Duchenne muscular dystrophy, where no dystrophin protein is produced, the dystrophin protein in BMD is partially functional, which explains the milder symptoms.

BMD is inherited in an X-linked recessive pattern. Since every male inherits an X chromosome from their mother and a Y chromosome from their father, each son born to a female with a dystrophin mutation on her X chromosome has a 50% chance of inheriting the flawed gene.

Because every female inherits one X chromosome from their mother and one from their father, they have a 50% chance of becoming a carrier if their mother carries the mutation.

Diagnosis

To diagnose Becker muscular dystrophy, a healthcare professional will begin by taking your and your family’s history and conducting a thorough physical exam.

During this exam, the healthcare professional tries to determine if your muscle weakness is caused by the muscle itself or by a neurological problem affecting the nerves that control the muscles.

To find the cause of the muscle weakness, your doctor may conduct several tests, including a blood test called a creatine kinase (CK) level and electromyography.

The CK level test looks for an elevated level of creatine kinase, an enzyme that leaks from damaged muscle. An elevated level indicates that the muscle is being destroyed by a process like muscular dystrophy or inflammation.

The electromyography test uses special needles inserted into the muscles to determine if nerve impulses are working normally. This can help narrow down the cause of the muscle weakness by indicating if the nerves are involved.

Genetic testing is also now widely available and can help doctors confirm the diagnosis with more certainty. DNA tests on the dystrophin gene can determine if the DMD gene is mutated and to what extent, thus helping to diagnose Becker muscular dystrophy or the more severe DMD mutation of Duchenne muscular dystrophy.

Treatment

While there is no cure for Becker muscular dystrophy and specific medical treatments are still being researched, many therapies can prolong life expectancy, improve your quality of life, and support you in remaining mobile and independent. These include:

Mobility aids: Braces or orthotics can be worn to support the ankle, knee, or legs. Some braces may be worn at night to keep the Achilles tendon stretched. Scooters and wheelchairs can help you maintain mobility and independence, especially when you need to cover long distances.

Cardiac care: If you have BMD, you should see a doctor for a cardiac evaluation on a frequent and regular basis so as to catch and treat deterioration of the heart muscle.

Physical and occupational therapy: A physical therapist can work with you to maintain your range of motion and postpone contractures. An occupational therapist can help by focusing on making everyday tasks, like driving or dressing, easier and more accessible.

Surgery: If contractures become severe, a tendon release procedure can help treat the immobility.

Anesthesia Warning

People with BMD can have unexpected reactions to anesthesia. If you have BMD, it’s important to let your doctor and surgical team know so that complications can be avoided or promptly treated.

Diet: While there are no dietary restrictions with BMD, it is recommended that you consume a diet high in fluid and fiber to avoid severe constipation, a common occurrence due to a lack of mobility and weak abdominal muscles.

A well-rounded diet with plenty of fresh fruits and vegetables can help you avoid constipation and weight gain. Obesity can put added stress on weak skeletal muscles and the heart, so staying within a healthy weight range is recommended.

Medications: Some medications that lessen the workload on the heart, like angiotensin-converting enzyme (ACE) inhibitors and beta blockers, have been shown to slow damage to the heart caused by BMD.

Though corticosteroids are sometimes prescribed for Duchenne muscular dystrophy, it is not as common in Becker muscular dystrophy. However, they are still prescribed for certain people.

Respiratory care: As you age with BMD and muscles of your lungs weaken, breathing can become more difficult, especially at night. A bilevel positive airway pressure (BiPAP) can help you breathe during sleep in a non-invasive way.

You may also experience weakened coughing muscles, which cause mucus to build up in your respiratory tract. A device called a cough assist can help.

Prognosis

The extent of disability when living with BMD is varied. Some people can walk with canes or braces, and others may need a wheelchair.

Most people with BMD live well into mid- to late adulthood. If there are no heart or breathing problems, most people can expect a normal or near normal life expectancy.

Coping

While doctors are a wealth of information in diagnosing and treating BMD, you may find that you have more questions for yourself or a loved one about how to navigate life with the disease. The Muscular Dystrophy Association can help by providing resources and one-on-one support via phone or email.

A Word From Verywell

Living with any chronic illness can feel overwhelming. Finding the right support—whether it’s peers who understand what you are going through, or a team of doctors and therapists who can help you manage your condition—is imperative.

Do not be afraid to ask for help or seek second opinions when it comes to your health.

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