Becker muscular dystrophy
Benign pseudohypertrophic muscular dystrophy; Becker's dystrophy
Becker muscular dystrophy is an inherited disorder that involves slowly worsening muscle weakness of the legs and pelvis.
Superficial muscles are close to the surface of the skin. Muscles which lie closer to bone or internal organs are called deep muscles.
Muscle tissue is composed primarily of contractile cells. Contractile cells have the ability to produce movement.
Tendons connect muscles to their bony origins and insertions.
The muscular components of the lower leg include the gastrocnemius, soleus, peroneus longus, tibialis anterior, extensor digitorum longus, and the Achilles tendon.
Causes
Becker muscular dystrophy is very similar to Duchenne muscular dystrophy. The main difference is that it gets worse at a much slower rate and it is less common. This disease is caused by a mutation in the gene that encodes a protein called dystrophin.
The disorder is passed down through families (inherited). Having a family history of the condition raises your risk.
Becker muscular dystrophy occurs in about 3 to 6 out of every 100,000 births. The disease is found mostly in boys.
Symptoms
Females rarely develop symptoms. Males will develop symptoms if they inherit the defective gene. Symptoms most often appear in boys between ages 5 and 15, but may begin later.
Muscle weakness of the lower body, including the legs and pelvis area, slowly gets worse, causing:
- Difficulty walking that gets worse over time; by age 25 to 30, the person is usually unable to walk
- Frequent falls
- Difficulty getting up from the floor and climbing stairs
- Difficulty with running, hopping, and jumping
- Loss of muscle mass
- Toe walking
- Muscle weakness in the arms, neck, and other areas is not as severe as in the lower body
Other symptoms may include:
- Breathing problems
- Cognitive problems (these do not get worse over time)
- Fatigue
- Loss of balance and coordination
Exams and Tests
The health care provider will do a nervous system (neurological) and muscle exam. A careful medical history is also important, because symptoms are similar to those of Duchenne muscular dystrophy. However, Becker muscular dystrophy gets worse much more slowly.
An exam may find:
- Abnormally developed bones, leading to deformities of the chest and back (scoliosis)
- Abnormal heart muscle function (cardiomyopathy)
- Congestive heart failure or irregular heartbeat (arrhythmia) - rare
- Muscle deformities, including contractures of heels and legs, abnormal fat and connective tissue in calf muscles
- Muscle loss that begins in the legs and pelvis, then moves to the muscles of the shoulders, neck, arms, and respiratory system
Tests that may be done include:
- CPK blood test
- Electromyography (EMG) nerve testing
- Muscle biopsy or genetic test
Treatment
There is no known cure for Becker muscular dystrophy. However there are many new drugs currently undergoing clinical testing that show significant promise in treating the disease. The current goal of treatment is to control symptoms to maximize the person's quality of life. Some providers prescribe steroids to help keep a patient walking for as long as possible.
Activity is encouraged. Inactivity (such as bed rest) can make the muscle disease worse. Physical therapy may be helpful to maintain muscle strength. Orthopedic appliances such as braces and wheelchairs may improve movement and self-care.
Abnormal heart function may require the use of a pacemaker.
Genetic counseling may be recommended. Daughters of a man with Becker muscular dystrophy will very likely carry the defective gene and could pass it on to their sons.
Support Groups
You can ease the stress of the illness by joining a muscular dystrophy support group where members share common experiences and problems.
Outlook (Prognosis)
Becker muscular dystrophy leads to slowly worsening disability. However, the amount of disability varies. Some people may need a wheelchair. Others may only need to use walking aids such as canes or braces.
Lifespan is most often shortened if there are heart and breathing problems.
Possible Complications
Complications may include:
- Heart-related problems such as cardiomyopathy
- Lung failure
- Pneumonia or other respiratory infections
- Increasing and permanent disability that leads to decreased ability to care for self, decreased mobility
When to Contact a Medical Professional
Call your provider if:
- Symptoms of Becker muscular dystrophy appear
- A person with Becker muscular dystrophy develops new symptoms (particularly fever with cough or breathing difficulties)
- You are planning to start a family and you or other family members have been diagnosed with Becker muscular dystrophy
Prevention
Genetic counseling may be advised if there is a family history of Becker muscular dystrophy.
References
Bharucha-Goebel DX. Muscular dystrophies. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 627.
Doughty CT, Amato AA. Disorders of skeletal muscle. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 109.
Gloss D, Moxley RT III, Ashwal S, Oskoui M. Practice guideline update summary: corticosteroid treatment of Duchenne muscular dystrophy: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2016;86(5):465-472. PMID: 26833937
Selcen D. Muscle diseases. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 393.
Version Info
Last reviewed on: 1/23/2022
Reviewed by: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
