Beckers Muscular Dystrophy

Information and facts about Eponymous diseases.

Becker's muscular dystrophy (also known as Benign pseudohypertrophic muscular dystrophy) is an X-linked recessive inherited disorder characterized by slowly progressive muscle weakness of the legs and pelvis.

It is a type of dystrophinopathy, which includes a spectrum of muscle diseases caused by mutations in the DMD gene, which encodes the protein dystrophin. Becker's muscular dystrophy is a milder form of Duchenne muscular dystrophy. Both Duchenne and Becker's muscular dystrophy are X-linked recessive diseases. Becker's is named after the German doctor Peter Emil Becker.

Genetics

The disorder is inherited with an X-linked recessive inheritance pattern. The gene is located on the X chromosome. Since women have two X chromosomes, if one X chromosome has the non-working gene, the second X chromosome will have a working copy of the gene to compensate. In these cases, some women have much milder symptoms because of this ability to compensate. For example, carrier females of mutations are at increased risk for dilated cardiomyopathy. Since men have an X and a Y chromosome and because they don't have another X to compensate for the defective gene, they will develop symptoms if they inherit the non-working gene.

All dystrophinopathes are inherited in an X-linked recessive manner. The risk to the siblings of an affected individual depends upon the carrier status of the mother. Carrier females have a 50% chance of passing the DMD mutation in each pregnancy. Sons who inherit the mutation will be affected; daughters who inherit the mutation will be carriers. Men who have Becker's musculary dystrophy can have children, and all their daughters are carriers, but none of the sons will inherit their father's mutation. Prenatal testing through amniocentesis or Chorionic villus sampling (CVS) for pregnancies at risk is possible if the DMD mutation is found in a family member or if informative linked markers have been identified.

Becker's muscular dystrophy occurs in approximately 3 to 6 in 100,000 male births. Symptoms usually appear in men at about age 12, but may sometimes begin later. The average age of becoming unable to walk is 25-30. Women rarely develop symptoms.

Genetic counseling is indicated for individuals or families who may carry this condition.

Symptoms

Muscle weakness, slowly progressive (Difficulty running, hopping, jumping; Progressive difficulty walking)
Ability to walk may continue into adulthood (up to age 40)
Frequent falls
Difficulty breathing
Cognitive dysfunction
Skeletal deformities, chest and back (scoliosis)
Muscle deformities (contractures of heels, legs; Pseudohypertrophy of calf muscles)
Fatigue
Heart disease
People with this disorder experience 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), but 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 (damage to the heart) does not occur as commonly with this disorder as it does with Duchenne's muscular dystrophy. Cognitive problems may accompany the disorder, but they are not inevitable and do not worsen as the disorder progresses.

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 may occur, but the development of congestive heart failure or arrhythmias (irregular heartbeats) is rare.

The ability to walk may continue to age 40 or older.
Creatine_kinase (CPK) levels may be elevated.
An electromyography (EMG) shows that weakness is caused by destruction of muscle tissue rather than by damage to nerves.
Genetic testing
A muscle biopsy or genetic test (blood test) confirms the diagnosis.

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 bed rest) 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 man with Becker's muscular dystrophy do not develop the disorder, but daughters may be carriers. The daughters' 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.

Expectations (prognosis)

Becker's muscular dystrophy results in slowly progressive disability. Death usually occurs in the fifth decade but some patients live to an advanced age.

Complications

Deformities
Permanent, progressive disability manifested as decreased mobility or decreased ability to care for self
Mental impairment
Cardiomyopathy
Pneumonia or other respiratory infections
Respiratory failure

Back to Eponymous diseases index page

Can't find what you are looking for?
Use our site search facility...

Home I Search Site I Site map I Conditions I Symptoms I News Archive I Forum I Contact us I About us I Access Keys

All information published on this web site is for information purposes only. The content of this web site should not be used for a conclusive diagnosis or for choosing a treatment. The content on this site has been provided as a guideline and general information it is not intended to replace professional medical care. In all serious cases it is advisable to recieve attention from a qualified medical practitioner. All text is available under the terms of the GNU free documentation license.