Becker Muscular Dystrophy

Becker muscular dystrophy is a rare inherited condition that causes progressive muscle weakness, primarily affecting the hips, thighs, shoulders, and heart. Though there is currently no cure, understanding the disease and working with a specialized care team can help maintain muscle function and improve quality of life.

Table of contents

• What is Becker muscular dystrophy?
• How common is this condition?
• What causes Becker muscular dystrophy?
• How is it inherited?
• Signs and symptoms
• How is it diagnosed?
• Treatment and management
• Outlook and prognosis
• Living with Becker muscular dystrophy

What is Becker muscular dystrophy?

Becker muscular dystrophy (BMD) is one of nine types of muscular dystrophies, which are genetic diseases that primarily affect voluntary muscles. The disease was named after German doctor Peter Emil Becker, who first described this variant in the 1950s^[1].

BMD belongs to a group of conditions called dystrophinopathies, which also includes Duchenne muscular dystrophy (DMD). The condition causes progressive muscle weakness and degeneration, meaning that muscles become weaker over time^[2]. The muscle weakness usually begins in the legs and pelvis and travels up the body over time^[2].

BMD is similar to Duchenne muscular dystrophy but allows the voluntary muscles to function better. It has a later onset and milder symptoms compared to DMD^[1]. However, the heart muscle can be affected similarly to the way it can be in DMD^[1].

• Muscles of the hips
• Pelvic area muscles
• Thigh muscles
• Shoulder muscles
• Heart muscle
• Breathing muscles

How common is this condition?

Becker muscular dystrophy is rare. It occurs in about 3 to 6 out of every 100,000 births^[2][5]. The condition mainly affects boys and men, though females who are carriers can sometimes have mild symptoms^[2].

After myotonic dystrophy and facioscapulohumeral dystrophy, BMD is probably the third most common type of muscular dystrophy found in adults^[2].

What causes Becker muscular dystrophy?

Until the 1980s, little was known about the cause of any kind of muscular dystrophy. In 1986, researchers supported by the Muscular Dystrophy Association identified the gene that, when flawed, causes both DMD and BMD. In 1987, the protein associated with this gene was identified and named dystrophin^[1].

BMD is caused by a change, called a mutation, in the gene that gives instructions for making dystrophin. The body needs dystrophin to stabilize muscle cells^[2]. This protein keeps the muscle cell membrane from breaking or tearing when muscles contract and relax^[1].

In BMD, the dystrophin protein that’s made from the gene is only partially functional. This means there is some dystrophin present, but not enough, or it doesn’t work as well as it should^[1][2]. This is different from Duchenne muscular dystrophy, where dystrophin is completely absent in muscle tissue^[2].

The change in the dystrophin gene results in less production of dystrophin or nonfunctional dystrophin, which causes muscle weakness and damage over time. Without enough working dystrophin, muscle cells are at risk for damage with normal use. Usually, the body will repair or replace damaged muscle cells. But in Becker muscular dystrophy, the cells die instead. After the muscle cells die, they are replaced by fat and scar tissue^[4].

How is it inherited?

Becker muscular dystrophy has X-linked recessive inheritance. This means the gene responsible for BMD is located on the X chromosome, one of two sex chromosomes^[2].

Because males have one X chromosome and thus only one copy of the gene, a mutation in their one copy is enough to cause BMD. This is why the condition almost exclusively affects males^[2].

Because females have two X chromosomes, a mutation generally needs to occur in both copies of the gene to cause the condition. Females who have a variant in one copy of the gene are called carriers. They usually don’t have symptoms, though approximately 22% of carriers may have mild symptoms such as cardiomyopathy or mild muscle weakness^[2][7].

Daughters of a man with Becker muscular dystrophy will very likely carry the defective gene and could pass it on to their sons^[5].

Signs and symptoms

BMD’s onset varies widely from 5 to 60 years of age, and the course is slower and less predictable than that of Duchenne muscular dystrophy^[1]. Symptoms most often appear between the ages of 5 and 15 years but may begin later^[2][7].

A child with Becker muscular dystrophy may start to walk later than most children do. However, the disease rarely causes health problems until muscle weakness develops in the hips and pelvis when the child is in their teens. Walking problems are usually noticed around age 15 to 16^[4].

Becker muscular dystrophy is progressive, meaning problems get worse with age. However, symptoms get worse slowly compared with Duchenne muscular dystrophy^[4].

Muscle-related symptoms

Generalized weakness first affects muscles of the hips, pelvic area, thighs, and shoulders^[1]. Common symptoms include:

• Difficulty walking that gets worse over time^[2]
• Difficulty walking up stairs^[2]
• Low tolerance for exercise^[2]
• Muscle pain and/or spasms^[2]
• Frequent falls^[2]
• Toe walking^[2]
• Fatigue^[2]
• Trouble lifting heavy loads^[4]
• More difficulty with sports^[4]
• Not being able to walk quickly, run smoothly, or maintain a running pace^[4]

Calf muscles are often enlarged. The calves may look bigger than normal, even though they’re weaker. This is called pseudohypertrophy, where enlarged muscle tissue is eventually replaced by fat and connective tissue^[1][4].

Muscle weakness in the arms, neck, and other areas is not as severe as in the lower body^[5]. Most people with BMD were found to remain able to walk until their 40s or older, though a small group experienced earlier loss of ability to walk^[3].

Heart problems

There can be significant heart involvement in BMD^[1]. The heart is made of muscle, so Becker muscular dystrophy can cause weakening of the heart muscle. This may lead to heartbeat irregularities and a condition called dilated cardiomyopathy, where the heart doesn’t pump blood as well as it should^[2][14].

Changes in the heart muscle may happen faster than in other muscles. Children who first show symptoms of Becker muscular dystrophy at younger ages are more likely to have heart problems than those whose symptoms start later^[4]. In some cases, dilated cardiomyopathy may be the first sign of Becker muscular dystrophy^[14].

Other symptoms

Additional symptoms may include:

• Breathing problems^[2]
• Learning differences^[2]
• Loss of balance and coordination^[2]
• Cognitive problems, though these do not get worse over time^[5]

Breathing muscles tend to stay strong enough that a ventilator or other mechanical breathing help isn’t usually needed^[4].

How is it diagnosed?

Doctors often diagnose muscular dystrophy based on the child’s family history, symptoms, and a physical examination^[4]. A careful medical history is important, because symptoms are similar to those of Duchenne muscular dystrophy^[5].

The examination will include a nervous system and muscle exam. An exam may find abnormally developed bones leading to deformities of the chest and back, abnormal heart muscle function, muscle deformities, and muscle loss that begins in the legs and pelvis^[5].

Diagnostic tests

Several tests are used to confirm the diagnosis:

Creatine kinase (CK) level: This blood test checks the level of creatine kinase, a protein that normally stays inside muscle cells. When muscular dystrophy damages muscle cells, they release CK into the blood. Elevated CK plasma level guides toward a potential diagnosis of Becker muscular dystrophy. People living with BMD may have up to 50 times the normal CK level^[4][14].

Electromyography (EMG): This test measures how well the muscles are working^[4][5].

Muscle biopsy: Doctors take a biopsy by removing a small piece of muscle tissue to examine under a microscope^[4][5].

Genetic testing: Diagnosis is confirmed with genetic testing which identifies the underlying mutation in the dystrophin gene^[14].

Heart tests: Tests such as an echocardiogram and electrocardiogram (ECG) may be performed to check heart function^[5].

Early diagnosis of Becker muscular dystrophy can aid in preserving muscle function and symptom management^[14].

Treatment and management

There is currently no known cure for Becker muscular dystrophy^[2][5]. The goal of treatment is to control symptoms to maximize quality of life^[5]. Management is supportive, with rehabilitative care essential to maintaining function long-term^[3].

As of 2019, most therapies are supportive in nature, although disease-modifying therapies are the subject of intense research^[9]. Several drugs designed to address the root cause are currently being studied, including gene therapy, glucocorticoids, and other medications^[6].

Medical treatments

Some healthcare providers prescribe steroids to help keep a patient walking for as long as possible^[5]. Early treatment includes steroid treatment that should be analyzed and personalized for each case^[8].

Early treatment of cardiomyopathy with ACE inhibitors is recommended, and referral for cardiac transplantation is appropriate in severe cases^[8]. Abnormal heart function may require the use of a pacemaker or defibrillator^[5].

Rehabilitation and therapy

Physical therapy: Physical therapy is helpful to maintain muscle strength and reduce joint contractures. It can help prolong walking ability. Activity is encouraged, as inactivity such as bed rest can make the muscle disease worse^[5][9]. The greatest physical therapy benefits may be derived from twice-weekly sessions of 30 to 45 minutes each^[12].

Occupational therapy: Activities of daily living skills are addressed, depending on the level of impairments. Specific adaptations may be provided to aid with dressing and bathroom skills^[12].

Speech therapy: Progressive weakness may lead to swallowing difficulties and an increased risk of aspiration pneumonia. A speech therapist may evaluate and provide recommendations^[12].

Assistive devices and equipment

Orthopedic appliances such as braces and wheelchairs may improve movement and self-care^[5]. Braces, also called orthoses, can support just the ankle and foot or extend over the knee. Ankle-foot orthoses are sometimes prescribed for night wear to keep feet from pointing downward and keep the Achilles tendon stretched^[9].

Mobility concerns are addressed, including the need for devices to assist with mobility, such as a scooter or a fully adapted wheelchair with a custom seat and back, custom supports, and electric power^[12].

Exercise guidelines

Research is starting to show that exercise can help the long-term health of patients with Becker. Movement, when performed safely, can be highly beneficial^[16]. However, patients with Becker need to be careful in their exercise because they are more prone to muscle loss and damage^[16].

Safe exercise practices include:

• Avoiding heavy weights and too much repetition^[16]
• Doing mild to moderate exercise^[16]
• Drinking plenty of water^[16]
• Not pushing to the point of exhaustion^[16]
• Resting after exercise^[16]
• Consulting your doctor before starting or incorporating a new exercise^[16]

Multidisciplinary care

Management includes multidisciplinary care with a specialized care team^[8][14]. A comprehensive, multidisciplinary team focuses on all aspects of neuromuscular disease in adults and children, providing diagnosis and treatment^[13]. This may include coordination of care with schools and other providers^[13].

Outlook and prognosis

Becker muscular dystrophy leads to slowly worsening disability. However, the amount of disability varies^[5]. BMD is slowly progressive with phenotypic variability. Despite childhood onset, independent walking is never lost before the third decade^[8].

Some people may need a wheelchair, while others may only need to use walking aids such as canes or braces. By age 25 to 30, many people are usually unable to walk^[5]. In a study involving 67 individuals with BMD, most remained able to walk until their 40s or older^[3].

Lifespan is most often shortened if there are heart and breathing problems^[5]. Thanks to general medical advances, particularly in cardiology, people with Becker muscular dystrophy are living longer in the 21st century than in previous decades^[9].

Possible complications may include:

• Heart-related problems such as cardiomyopathy^[5]
• Lung failure^[5]
• Pneumonia or other respiratory infections^[5]
• Increasing and permanent disability that leads to decreased ability to care for self and decreased mobility^[5]

Muscle loss is irreversible, which makes maintaining muscle function an important part of managing the condition^[14].

Living with Becker muscular dystrophy

It is possible to lead a fulfilling life with Becker muscular dystrophy. A specialized care team can play a critical role in managing the condition and improving quality of life^[14].

Being proactive in the management of Becker muscular dystrophy is very important as it’s a progressive disorder. The earlier you act, the more you may be able to minimize symptoms and mitigate the challenges that may arise^[14].

Sharing your diagnosis

Accepting an initial diagnosis of a disability can be a challenging and emotional process. However, the people who love you will be there to support you if you reach out. Letting people in lightens the load, and accepting support from family and loved ones can make a significant difference^[18].

Adapting to changes

The biggest challenge for many people on their journey has been to accept the lifestyle changes that a progressive disease brings and try to find new ways to live life to the fullest. Over time, it may be necessary to give up certain hobbies or activities. The key is to try not to regret what you are no longer able to do and embrace the things you are still able to do. This life lesson goes hand-in-hand with the idea of focusing on the things you can control and accepting the things you cannot control^[18].

Community support

Support from family and the community of people affected by neuromuscular disease can be invaluable. Joining a muscular dystrophy support group where members share common experiences and problems can ease the stress of the illness^[5].

Practical considerations

It’s important to ensure that even within the context of Becker, individuals are doing things appropriate for their age and stage of life. Together with the community and care team, it’s all about figuring out how to make that happen^[15].

Educational objectives for patients and families include teaching techniques for energy conservation, joint protection, and the prevention of overuse fatigue. Anticipatory guidance is ongoing, with work-related concerns during adult years being primary issues. Work modification scenarios and the use of assistive devices are prominent concerns^[12].

Genetic counseling

Genetic counseling may be recommended for families. This can help families understand the inheritance pattern and the risk of passing the condition to future children^[5].

A diagnosis of muscular dystrophy doesn’t mean you can’t go on to live a very full and rewarding life. Many patients are living proof of that^[19].