Muscular dystrophy

Definition

Muscular dystrophy is a group of inherited disorders that involve muscle weakness and loss of muscle tissue, which get worse over time.

Alternative Names

Inherited myopathy, MD

Causes, incidence, and risk factors

Muscular dystrophies, or MD, are a group of inherited conditions, which means they are passed down through families. They may occur in childhood or adulthood. There are many different types of muscular dystrophy. They include:

• Becker muscular dystrophy
• Duchenne muscular dystrophy
• Emery-Dreifuss muscular dystrophy
• Facioscapulohumeral muscular dystrophy
• Limb-girdle muscular dystrophy
• Myotonia congenita
• Myotonic dystrophy

Symptoms

Symptoms vary with the different types of muscular dystrophy.

All of the muscles may be affected. Or, only specific groups of muscles may be affected, such as those around the pelvis, shoulder, or face. Muscular dystrophy can affect adults, but the more severe forms tend to occur in early childhood.

Symptoms include:

• Mental retardation (only present in some types of the condition)
• Muscle weakness that slowly gets worse
  • Delayed development of muscle motor skills
  • Difficulty using one or more muscle groups
  • Drooling
  • Eyelid drooping (ptosis)
  • Frequent falls
  • Loss of strength in a muscle or group of muscles as an adult
  • Loss in muscle size
  • Problems walking (delayed walking)

Signs and tests

A physical examination and your medical history will help the doctor determine the type of muscular dystrophy. Specific muscle groups are affected by different types of muscular dystrophy.

The doctor's exam may show:

• Abnormally curved spine (scoliosis)
• Joint contractures (clubfoot, clawhand, or others)
• Low muscle tone (hypotonia)

Some types of muscular dystrophy involve the heart muscle, causing cardiomyopathy or disturbed heart rhythm (arrhythmias).

Often, there is a loss of muscle mass (wasting), which may be hard to see because some types of muscular dystrophy cause a build-up of fat and connective tissue that makes the muscle appear larger. This is called pseudohypertrophy.

A muscle biopsy may be used to confirm the diagnosis. In some cases, a DNA blood test may be all that is needed.

Other tests may include:

• Heart testing - electrocardiography (ECG)
• Nerve testing - electromyography (EMG)
• Blood testing - including CPK level
• Genetic testing for some forms of muscular dystrophy

This disease may also alter the results of the following tests:

• Aldolase
• AST
• Creatinine
• LDH
• Myoglobin - urine and blood

Treatment

There are no known cures for the various muscular dystrophies. The goal of treatment is to control symptoms.

Physical therapy may help patients maintain muscle strength and function. Orthopedic appliances such as braces and wheelchairs can improve mobility and self-care abilities. In some cases, surgery on the spine or legs may help improve function.

Corticosteroids taken by mouth are sometimes prescribed to children to keep them walking for as along as possible.

The person should be as active as possible. Complete inactivity (such as bedrest) can make the disease worse.

Support Groups

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

See: Muscular dystrophy - support group

Expectations (prognosis)

The severity of disability depends on the type of muscular dystrophy. All types of muscular dystrophy slowly get worse, but how fast this happens varies widely.

Some types of muscular dystrophy, such as Duchenne muscular dystrophy, are deadly. Other types cause little disability and people with them have a normal lifespan.

Complications

• Cardiomyopathy
• Decreased ability to care for self
• Decreased mobility
• Lung failure
• Tightening of muscles around the joints (contractures)
• Mental impairment (varies)
• Scoliosis

Calling your health care provider

Call your health care provider if:

• You have symptoms of muscular dystrophy.
• You have a personal or family history of muscular dystrophy and you are planning to have children.

Prevention

Genetic counseling is advised when there is a family history of muscular dystrophy. Women may have no symptoms but still carry the gene for the disorder. Duchenne muscular dystrophy can be detected with about 95% accuracy by genetic studies performed during pregnancy.

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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.