Becker Muscular Dystrophy (BMD)
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What is Becker muscular dystrophy?
Becker muscular dystrophy (BMD) is a rare, inherited condition that results in progressive muscle degeneration and muscle weakness. It almost exclusively affects people assigned male at birth due to its X-linked inheritance (passed on through the mother, who is a carrier).
The muscle weakness usually begins in your legs and pelvis and travels up your body over time.
After myotonic dystrophy and facioscapulohumeral dystrophy, BMD is probably the third most common type of muscular dystrophy found in adults.
What is the difference between Becker muscular dystrophy and Duchenne muscular dystrophy?
Both Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD) are caused by changes (mutations) in the gene that gives instructions for a protein called dystrophin, which is important for muscle function.
In DMD, dystrophin is completely absent in muscle tissue, while in BMD, there’s some — but not enough — dystrophin present.
Becker muscular dystrophy is less common and less severe than Duchenne muscular dystrophy. The symptoms of the two conditions are similar, but Becker muscular dystrophy gets worse much more slowly.
Who does Becker muscular dystrophy affect?
Becker muscular dystrophy (BMD) mainly affects people assigned male at birth, but people assigned female at birth who are carriers for BMD can sometimes have symptoms, which are usually mild.
Symptoms most often appear between the ages of 5 and 15 years but may begin later.
How common is Becker muscular dystrophy?
Becker muscular dystrophy is rare. It occurs in about 3 to 6 out of every 100,000 births and mainly affects children assigned male at birth.
Symptoms and Causes
What are the symptoms of Becker muscular dystrophy?
Symptoms of Becker muscular dystrophy (BMD) most often start between the ages of 5 and 15 years but may begin later.
BMD causes muscle weakness that gets worse over time, so common symptoms include:
- Difficulty walking up stairs.
- Difficulty walking that gets worse over time.
- Low tolerance for exercise.
- Muscle pain and/or spasms.
- Frequent falls.
- Toe walking.
Other symptoms of BMD may include:
- Breathing problems.
- Learning differences.
- Loss of balance and coordination.
People assigned female at birth who are carriers of BMD may only have cardiomyopathy or mild muscle weakness. Approximately 22% of carriers have symptoms, but they vary greatly.
What causes Becker muscular dystrophy?
Becker muscular dystrophy (BMD) is in inherited condition. It’s caused by a change (mutation) in the gene that gives instructions for a protein called dystrophin. Your body needs dystrophin to stabilize muscle cells.
A change in the dystrophin gene results in nonfunctional or less production of dystrophin, which causes muscle weakness and damage over time.
How is Becker muscular dystrophy inherited?
Becker muscular dystrophy (BMD) has X-linked recessive inheritance.
X-linked means the gene responsible for BMD is located on the X chromosome, one of two sex chromosomes. Genes, like chromosomes, usually come in pairs. Recessive means that when there are two copies of the responsible gene, both copies must have a disease-causing change (pathogenic variant or mutation) for a person to have the condition.
Because people assigned male at birth (AMAB) have one X chromosome and thus only one copy of the gene, a pathogenic variant in their one copy is enough to cause BMD.
Because people assigned female at birth (AFAB) have two X chromosomes, a pathogenic variant for an X-linked recessive disease generally needs to occur in both copies of the gene to cause the condition. People AFAB who have a variant in one copy of the gene are called carriers. In rare cases, people AFAB who are carriers may experience mild to moderate symptoms, but most have no symptoms.
A person AFAB who carries one X-linked gene variant has a 50% chance of having a son with BMD and a 50% chance of having a daughter who is a carrier. A person AMAB with BMD can’t pass it on to their sons, but all of their daughters will be carriers.
Diagnosis and Tests
How is Becker muscular dystrophy diagnosed?
If you or your child are experiencing symptoms of Becker muscular dystrophy, your healthcare provider will likely perform a physical exam, neurological exam and muscle exam. They’ll ask detailed questions about your symptoms and medical history.
During the exams, they may find:
- Muscle loss in your legs and pelvis.
- Excessive muscle bulk in your calves (pseudohypertrophy).
- Spinal curvature (scoliosis) and deformities of your chest.
- Muscle abnormalities, including contractures (permanent tightening of your muscles, tendons and skin) of your heels and legs.
What tests will be done to diagnose Becker muscular dystrophy?
If your provider suspects that you or your child may have Becker muscular dystrophy, they’ll likely order the following tests:
- Creatine kinase blood test: Your muscles release creatine kinase when they’re damaged. A creatine kinase level that’s raised five times or more above normal may be seen with BMD.
- Genetic blood test: A genetic blood test that looks for a change in the dystrophin gene can confirm the diagnosis of BMD.
If you or your child has BMD, your provider may also recommend an electrocardiogram (EKG) and echocardiogram to check for any heart muscle issues that BMD can cause.
Management and Treatment
How is Becker muscular dystrophy treated?
There’s currently no cure for Becker muscular dystrophy (BMD), so the main goal of treatment is to manage symptoms and optimize quality of life.
The two main forms of treatment for BMD include:
- Corticosteroids: Corticosteroids, such as prednisolone, are beneficial for improving lung function, delaying scoliosis, delaying the onset of cardiomyopathy and prolonging survival.
- Rehabilitation: Rehabilitation can help prolong mobility and improve quality of life. Physical therapy can help strengthen muscles, and speech therapy, occupational therapy and recreational therapy can help with performing daily tasks.
Other supportive therapies for BMD include:
- Mobility aids, such as braces, canes and wheelchairs.
- Medication (ACE inhibitors and beta-blockers) to treat cardiomyopathy.
- Surgery to help treat scoliosis and contractures.
- Tracheostomy and assisted ventilation for respiratory failure.
There are many new drugs currently undergoing clinical testing that show promise in treating BMD.
Can Becker muscular dystrophy be prevented?
Since Becker muscular dystrophy (BMD) is an inherited condition, there’s nothing you can do to prevent it.
If you have BMD, or if you’re concerned about the risk of passing on BMD or other genetic conditions before trying to have a biological child, talk to your healthcare provider about genetic counseling.
Outlook / Prognosis
What is the prognosis of Becker muscular dystrophy?
The prognosis (outlook) of Becker muscular dystrophy (BMD) varies. BMD leads to slowly worsening disability, but the severity of disability varies. Some people may need a wheelchair, while others may only need to use walking aids such as canes or braces.
If a person with BMD has heart or breathing issues, their lifespan may be shortened.
Possible complications of BMD include:
- Heart-related problems such as cardiomyopathy.
- Respiratory difficulty from weakness of breathing muscles.
- Pneumonia or other respiratory infections.
- Increasing and permanent disability that leads to a decreased ability to care for yourself.
- Bone fractures.
What is the life expectancy of Becker muscular dystrophy?
The average life expectancy of a person with Becker muscular dystrophy is somewhat shortened and is about 40 to 50 years. Dilated cardiomyopathy (weakening of your heart muscles) is the most common cause of death.
How do I take care of myself or someone with Becker muscular dystrophy?
If you have Becker muscular dystrophy (BMD), it’s essential to ensure you’re getting quality medical care to prevent or treat complications of BMD, such as heart and breathing issues. You may also want to consider joining a support group to meet others who can relate to your experiences.
If you’re taking care of someone with BMD, it’s important to advocate for them to ensure they get the best medical care and access to mobility devices and therapy that can help them be more independent.
When should I see my healthcare provider about Becker muscular dystrophy?
If you (or your child) have been diagnosed with Becker’s muscular dystrophy, you’ll need to see your team of healthcare providers regularly to receive treatment and monitor symptoms.
A note from Cleveland Clinic
Understanding your (or your child’s) diagnosis of Becker muscular dystrophy diagnosis can be overwhelming. Your healthcare team will offer a robust management plan that’s unique to your symptoms. It’s important to make sure you receive the support needed and are attentive to your health.
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