Becker’s Muscular Dystrophy (BMD) is a form of muscular dystrophy - a group of inherited disorders that ultimately lead to progressively weakened muscles and loss of function.
What are the other Names for this Condition? (Also known as/Synonyms)
- BMD (Becker Muscular Dystrophy)
- Benign Juvenile Muscular Dystrophy
- Progressive Tardive Muscular Dystrophy
What is Becker’s Muscular Dystrophy? (Definition/Background Information)
- Becker’s Muscular Dystrophy (BMD) is a form of muscular dystrophy - a group of inherited disorders that ultimately lead to progressively weakened muscles and loss of function
- In BMD, the skeletal muscles used for movement and muscles of the heart, are primarily affected. This condition develops slowly in a child and by the young-adult phase, individuals would have fully developed severe muscles weaknesses, including walking difficulties
- BMD is very similar to Duchenne muscular dystrophy (DMD) - both disorders are caused by a defective gene, called dystrophin gene. This particular gene manufactures dystrophin proteins in the muscle, where they play a role in maintaining the muscle’s structure
- Individuals with this defect, either have dystrophin with altered structures and activity, or do not make the proteins at all. A genetic test or a muscle biopsy can enable a definitive diagnosis of BMD in most cases
- Often symptomatic treatment is provided for this incurable condition affecting the muscles. This includes physical therapy, surgery, and the use of assistive devices that is usually required for the rest of one’s life
Who gets Becker’s Muscular Dystrophy? (Age and Sex Distribution)
- Males are predominantly affected by Becker’s Muscular Dystrophy, an X-linked recessive disorder. This means the mutated gene causing BMD is found on the X-chromosome. Every male inherits one X chromosome and one Y chromosome
- BMD mostly affects older boys and young men. Individuals with BMD, typically encounter symptoms near the age of 11 years. By the age of 25-30 years, most patients lose their ability to walk and require assistive devices for mobility
- Females, in contrast, receive two X-chromosomes. BMD is found more frequently in males, because if the ‘sole’ X-chromosome that they receive is defective, they develop BMD. However, in the case of females, inheriting one abnormal X-chromosome, it will not necessarily lead to BMD, since the second X-chromosome can still function correctly
- “Carriers” are females, who have one X-chromosome with a defective gene, but a functioning second X-chromosome. Generally, females, including carriers, do not experience signs and symptoms of BMD
What are the Risk Factors for Becker’s Muscular Dystrophy? (Predisposing Factors)
- One risk factor associated with Becker’s Muscular Dystrophy is having a family history of the condition
- There are instances, however, where new mutations arise in the dystrophin gene, leading to BMD in individuals with no family history of the disorder
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Becker’s Muscular Dystrophy? (Etiology)
- Becker’s Muscular Dystrophy is caused by a mutation, or abnormality, in the dystrophin gene found on the X-chromosome
- Although the mutation for BMD is on the same gene that leads to Duchenne muscular dystrophy, each condition is due to a different mutation on the gene
- The dystrophin gene is responsible for the production of dystrophin, a muscle protein that supports muscle fibers and keeps them from being injured during muscle movement. Dystrophin is also found in the heart
- Typically, with Becker’s Muscular Dystrophy, a mutation in the dystrophin gene produces abnormal and dysfunctional dystrophin proteins. As a result, BMD patients have muscle cells that progressively become damaged, causing weakened muscles
What are the Signs and Symptoms of Becker’s Muscular Dystrophy?
Symptoms of Becker’s Muscular Dystrophy (BMD) typically appear around the age of 11 years. In some cases, they can arise later in one’s life too. Most individuals with BMD lose the ability to walk, near the age of 25-30 years.
The signs and symptoms of BMD include:
- Muscle weakness, especially in the pelvis area and lower region; weakness can occur in the arms and neck as well
- Progressive difficulty walking
- Frequent falls
- Difficulty with motor skills, including jumping, hopping, and running
- Cognitive problems
How is Becker’s Muscular Dystrophy Diagnosed?
The diagnosis of Becker’s Muscular Dystrophy may include the following tests and exams:
- With Becker’s Muscular Dystrophy, and all other forms of muscular dystrophy, a physician will check the family history for muscle disease, as well as complete a thorough physical exam of the individual
- A creatine kinase test can be used to measure the amount of creatine kinase in blood. The enzyme, creatine kinase, is released by the muscle and into the bloodstream, when any deterioration has occurred. High levels of creatine kinase indicate some type of muscle disease, which can help physicians in narrowing down the possible conditions or disorder that the affected individual might have
- Genetic testing:
- This method uses blood samples to study the dystrophin gene and to determine the presence or absence of mutations
- To diagnose BMD, a genetic test can detect areas of the dystrophin gene, where either duplication or deletion mutations have occurred
- Approximately two-thirds of individuals with BMD are diagnosed by genetic tests that can help identify these duplications or deletions
- Muscle biopsy:
- If a genetic test does not show any signs of the presence of BMD, a muscle biopsy may be performed
- In a muscle biopsy, a muscle sample from an individual is removed and examined under a microscope
- This technique can help to distinguish BMD from other diseases by identifying any abnormal changes in the structure of the muscle cells
- Tests that stain the muscle sample can be used to visualize any muscle proteins present
- Electromyogram (EMG):
- Another diagnostic test that can be used is the EMG, which is a tool to study the muscles and the nerves that control them
- In an EMG, a needle is placed into the muscle, which allows physicians to study the muscle’s electrical activity and its response to stimulation of the nerves supplying it
- An EMG can help diagnose a muscle disease, as opposed to a condition related to the nerves
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Becker’s Muscular Dystrophy?
The possible complications associated with Becker’s Muscular Dystrophy include:
- Cardiomyopathy, or the enlargement and weakening of the heart
- Pneumonia, respiratory infections
- Contractures - fixations in the muscles and joints, leading to reduced flexibility and abnormal movement
- Pseudohypertrophy: Fat and connective tissue found in calf muscles, enlarging these muscles
- Scoliosis: Spinal abnormalities affecting the chest and back
- Lung failure
How is Becker’s Muscular Dystrophy Treated?
Presently, there is no cure available for Becker’s Muscular Dystrophy. However, symptomatic treatment methods may be provided that include:
- Physical therapy is recommended for patients suffering from muscular dystrophy to keep muscles and joints flexible. This can help in slowing the development of contractures, or reduced flexibility in the muscles and joints
- Surgery is another treatment option for individuals with BMD. For individuals with severe contractures, having surgery, involves the release of tension within the tightened muscles
- Assistive devices are helpful for BMD patients to maintain their mobility:
- Braces can be used to delay the progression of contractures by keeping muscles stretched
- Also, wheelchairs and canes are often utilized to allow BMD patients to care for themselves and to maintain independence
How can Becker’s Muscular Dystrophy be Prevented?
- Currently, there are no specific methods or guidelines to prevent Becker’s Muscular Dystrophy genetic condition
- Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
- If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders
What is the Prognosis of Becker’s Muscular Dystrophy? (Outcomes/Resolutions)
- Becker’s Muscular Dystrophy leads to slow muscle deterioration. In most BMD patients, the symptoms are first observed around the age of 11 years. In some, they may appear later than this
- By the age of around 25-30 years, a majority of individuals have difficulty walking and ultimately lose their ability to walk. The use of braces, wheelchairs, or canes, however, can address some of the issues related to mobility
- Overall, the symptoms and severity of the symptoms of Becker’s Muscular Dystrophy vary from one individual to another
Additional and Relevant Useful Information for Becker’s Muscular Dystrophy:
- The difference between Becker’s Muscular Dystrophy (BMD) and Duchenne’s Muscular Dystrophy (DMD) is that BMD is a milder condition as it occurs at a slower rate
- Like DMD, BMD is an X-linked recessive disorder and mostly affects males. Between 3-6 out of every 100,000 males have BMD, making it less frequently encountered than DMD
- Although BMD and DMD share similar symptoms, children with BMD do not typically experience them until age 11, while the onset of symptoms for children with DMD is before the age of 6 years
- Moreover, the symptoms of BMD display variation among individuals with the condition
What are some Useful Resources for Additional Information?
References and Information Sources used for the Article:
http://ghr.nlm.nih.gov/condition/duchenne-and-becker-muscular-dystrophy (accessed on 11/13/15)
http://www.nlm.nih.gov/medlineplus/ency/article/000706.htm (accessed on 11/13/15)
http://www.mayoclinic.com/health/muscular-dystrophy/DS00200 (accessed on 11/13/15)
http://my.clevelandclinic.org/disorders/muscular_dystrophy/hic_muscular_dystrophy.aspx (accessed on 11/13/15)
Helpful Peer-Reviewed Medical Articles:
Chakkalakal, J. V., Thompson, J., Parks, R. J., & Jasmin, B. J. (2005). Molecular, cellular, and pharmacological therapies for Duchenne/Becker muscular dystrophies. FASEB J, 19(8), 880-891. doi: 10.1096/fj.04-1956rev
Finsterer, J., & Stollberger, C. (2008). Cardiac involvement in Becker muscular dystrophy. Can J Cardiol, 24(10), 786-792.
Kaspar, R. W., Allen, H. D., & Montanaro, F. (2009). Current understanding and management of dilated cardiomyopathy in Duchenne and Becker muscular dystrophy. J Am Acad Nurse Pract, 21(5), 241-249. doi: 10.1111/j.1745-7599.2009.00404.x
Takagi, A., & Nakase, H. (2008). Malignant hyperthermia-like reactions in Duchenne or Becker muscular dystrophy: review and hypothesis. Rinsho Shinkeigaku, 48(2), 101-105.
Tselikas, L., Rodrigues, E., Jammal, M., Tiev, K., Chayet, C., Josselin-Mahr, L., . . . Kettaneh, A. (2011). [Late onset Becker muscular dystrophy. A case report and literature review]. Rev Med Interne, 32(3), 181-186. doi: 10.1016/j.revmed.2010.10.353.
Finsterer, J., & Stöllberger, C. (2001). Spontaneous left ventricular hypertrabeculation in dystrophin duplication based Becker's muscular dystrophy. Herz, 26(7), 477-481.
Wagner, K. R., Hamed, S., Hadley, D. W., Gropman, A. L., Burstein, A. H., Escolar, D. M., ... & Fischbeck, K. H. (2001). Gentamicin treatment of Duchenne and Becker muscular dystrophy due to nonsense mutations. Annals of neurology, 49(6), 706-711.
Aartsma‐Rus, A., Van Deutekom, J. C., Fokkema, I. F., Van Ommen, G. J. B., & Den Dunnen, J. T. (2006). Entries in the Leiden Duchenne muscular dystrophy mutation database: An overview of mutation types and paradoxical cases that confirm the reading‐frame rule. Muscle & nerve, 34(2), 135-144.