Becker's muscular dystrophy

Causes and Risks:
Becker's muscular dystrophy is very similar to Duchenne's muscular dystrophy , except that it progresses at a much slower rate. The disorder is inherited with an X-linked recessive inheritance pattern--the gene is located on the X chromosome. Men will develop symptoms if the female transmits the gene for the disorder. Women may be carriers of the gene.

There is progressive muscle weakness of the legs and pelvis which is associated with a loss of muscle mass ( wasting ). Muscle weakness also occurs in the arms, neck, and other areas, but not as severely as in the lower half of the body. Calf muscles initially enlarge (an attempt by the body to compensate for loss of muscle strength), the enlarged muscle tissue is eventually replaced by fat and connective tissue (pseudohypertrophy). Muscle contractures occur in the legs and heels, causing inability to use the muscles because of shortening of muscle fibers and fibrosis of connective tissue. Bones develop abnormally, causing skeletal deformities of the chest and other areas. Cardiomyopathy occurs in almost all cases. Mental retardation may accompany the disorder but it is not inevitable and does not worsen as the disorder progresses. The cause of this impairment is unknown.

Becker's muscular dystrophy occurs in approximately 3 out of 100,000 people. Symptoms usually appear in men between the ages of 7 and 26. Women rarely develop symptoms. Because this is an inherited disorder, risks include having a family history of Becker's muscular dystrophy.

Prevention:
Genetic counseling may be advised if there is a family history of Becker's muscular dystrophy.

Symptoms:
  • muscle weakness , slowly progressive
  • frequent falls
  • difficulty with muscle skills (running, hopping, jumping)
  • progressive difficulty walking
    • loss of walking ability occurs slowly
    • ability to walk may continue into adulthood (up to age 40)

  • intellectual retardation
  • skeletal deformities, chest and back ( scoliosis )
  • muscle deformities - contractures of heels, legs
    • pseudohypertrophy of calf muscles

  • fatigue



Signs and Tests:
The pattern of symptom development resembles that of Duchenne's muscular dystrophy , but with a much slower rate of progression. Muscle wasting begins in the legs and pelvis, then progresses to the muscles of the shoulders and neck, followed by loss of arm muscles and respiratory muscles. Calf muscle enlargement (pseudohypertrophy) is quite obvious. Cardiomyopathy is commonly present but development of congestive heart failure or arrhythmias (irregular heartbeats) is rare. The ability to walk may continue to age 40 or more.



Treatment:
There is no known cure for Becker's muscular dystrophy. Treatment is aimed at control of symptoms to maximize the quality of life.

Activity is encouraged. Inactivity (such as bedrest) can worsen the muscle disease. 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 advisable. Sons of a male with Becker's muscular dystrophy do not develop the disorder, but daughters may be carriers and the daughter's sons may develop the disorder.

Support Groups:
The stress of illness can often be helped by joining a support group where members share common experiences and problems. See muscular dystrophy - support group .

Prognosis:
Becker's muscular dystrophy results in slowly progressive disability. A normal life span is possible; however, death usually occurs after age 40.

Complications:



Call Your Healthcare Provider:
Call for an appointment with your health care provider if symptoms indicate Becker's muscular dystrophy may be present.

Call your health care provider if a person with Becker's muscular dystrophy develops new symptoms, particularly fever with cough or breathing difficulties .

Call for an appointment with your health care provider if planning a family and Becker's muscular dystrophy has been diagnosed in self or family members.