Becker muscular dystrophy

Definition

Becker muscular dystrophy is an inherited disorder that involves slowly worsening muscle weakness of the legs and pelvis.

Alternative Names

Benign pseudohypertrophic muscular dystrophy; Becker's dystrophy

Causes, incidence, and risk factors

Becker muscular dystrophy is very similar to Duchenne muscular dystrophy, except that it gets worse at a much slower rate.

The disorder is passed down through families (inherited). Having a family history of the condition raises your risk.

Becker muscular dystrophy occurs in approximately 3 - 6 out of every 100,000 males. It is less common than Duchenne muscular dystrophy.

Symptoms

Females rarely develop symptoms. Males will develop symptoms if they inherit the defective gene. Symptoms usually appear in boys at about age 12, 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 25-30 the person is usually unable to walk
• Frequent falls
• Difficulty with running, hopping, and jumping
• Loss of muscle mass

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

Signs and tests

The health care provider will do a nervous system (neurological) and muscle examination. A careful medical history is also important, because the pattern of symptom development resembles that of Duchenne's 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)
• Abnormality of heart muscle function (cardiomyopathy)
• Congestive heart failure or irregular heartbeat (arrhythmias) - 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 on 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 blood test

Treatment

There is no known cure for Becker muscular dystrophy. The goal of treatment is to control symptoms to maximize the person's quality of life. Some doctors 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 mobility and self-care.

Genetic counseling may be recommended. Daughters of a man with Becker muscular dystrophy may carry the defective gene and could pass it onto their sons.

Support Groups

You can ease the stress of illness by joining a support group where members share common experiences and problems.

See: Muscular dystrophy - support group

Expectations (prognosis)

Becker muscular dystrophy leads to slowly worsening disability, although the degree of disability varies. Some men may need a wheelchair, while others may only need to use walking aids such as canes or braces.

Complications

• Heart-related complications 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

Calling your health care provider

Call your health care 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.

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References

Kliegman RM, Behrman RE, Jenson HB, Stanton BF. Muscular dystrophies. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 608.