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Duchenne muscular dystrophy

Pseudohypertrophic muscular dystrophy; Muscular dystrophy - Duchenne type

 

Duchenne muscular dystrophy is an inherited disorder. It involves muscle weakness , which quickly gets worse.

Causes

 

Duchenne muscular dystrophy is a form of muscular dystrophy . It worsens quickly. Other muscular dystrophies (including Becker's muscular dystrophy ) get worse much more slowly.

Duchenne muscular dystrophy is caused by a defective gene for dystrophin (a protein in the muscles). However, it often occurs in people without a known family history of the condition.

The condition most often affects boys due to the way the disease is inherited. The sons of women who are carriers of the disease (women with a defective gene, but no symptoms themselves) each have a 50% chance of having the disease. The daughters each have a 50% chance of being carriers. Very rarely, a female can be affected by the disease.

Duchenne muscular dystrophy occurs in about 1 out of every 3,600 male infants. Because this is an inherited disorder, risks include a family history of Duchenne muscular dystrophy.

 

Symptoms

 

Symptoms most often appear before age 6. They may come on as early as infancy. Most boys show no symptoms in the first few years of life.

Symptoms may include:

  • Fatigue
  • Learning difficulties (the IQ can be below 75)
  • Intellectual disability (possible, but does not get worse over time)

Muscle weakness:

  • Begins in the legs and pelvis, but also occurs less severely in the arms, neck, and other areas of the body
  • Problems with motor skills (running, hopping, jumping)
  • Frequent falls
  • Trouble getting up from a lying position or climbing stairs
  • Weakness quickly gets worse

Progressive difficulty walking :

  • Ability to walk may be lost by age 12, and the child will have to use a wheelchair.
  • Breathing difficulties and heart disease usually start by age 20.

 

Exams and Tests

 

A complete nervous system (neurological), heart, lung, and muscle exam may show:

  • Abnormal heart muscle ( cardiomyopathy )
  • Congestive heart failure or irregular heart rhythm ( arrhythmia )
  • Deformities of the chest and back ( scoliosis )
  • Enlarged muscles of the calves, buttocks, and shoulders (around age 4 or 5). These muscles are eventually replaced by fat and connective tissue (pseudohypertrophy).
  • Loss of muscle mass ( wasting )
  • Muscle contractures in the heels, legs
  • Muscle deformities
  • Respiratory disorders, including pneumonia and swallowing with food or fluid passing into the lungs (in late stages of the disease)

Tests may include:

  • Electromyography ( EMG )
  • Genetic tests
  • Muscle biopsy
  • Serum CPK

 

Treatment

 

There is no known cure for Duchenne muscular dystrophy. Treatment aims to control symptoms to improve quality of life.

Steroid drugs can slow the loss of muscle strength. They may be started when the child is diagnosed or when muscle strength begins to decline.

Other treatments may include:

  • Albuterol, a drug used for people with asthma
  • Amino acids
  • Carnitine
  • Coenzyme Q10
  • Creatine
  • Fish oil
  • Green tea extracts
  • Vitamin E

However, the effects of these treatments have not been proven. Stem cells and gene therapy may be used in the future.

The use of steroids and the lack of physical activity can lead to excessive weight gain. Activity is encouraged. Inactivity (such as bedrest) can make the muscle disease worse. Physical therapy may help to maintain muscle strength and function. Speech therapy is often needed.

Other treatments may include:

  • Assisted ventilation (used during the day or night)
  • Drugs to help heart function, such as angiotensin converting enzyme inhibitors, beta blockers, and diuretics
  • Orthopedic appliances (such as braces and wheelchairs) to improve mobility
  • Proton pump inhibitors (for people with gastroesophageal reflux)

Several new treatments are being studied in trials.

 

Support Groups

 

You can ease the stress of illness by joining a support group where members share common experiences and problems. The Muscular Dystrophy Association is an excellent source of information on this disease.

 

Outlook (Prognosis)

 

Duchenne muscular dystrophy leads to progressively worsening disability. Death often occurs by age 25, typically from lung disorders. However, advances in supportive care have resulted in many men living much longer than this.

 

Possible Complications

 

Complications may include:

  • Cardiomyopathy (can also occur in female carriers, who should also be screened)
  • Congestive heart failure (rare)
  • Deformities
  • Heart arrhythmias (rare)
  • Mental impairment (varies, usually minimal)
  • Permanent, progressive disability, including decreased mobility and decreased ability to care for self
  • Pneumonia or other respiratory infections
  • Respiratory failure

 

When to Contact a Medical Professional

 

Call your health care provider if:

  • Your child has symptoms of Duchenne muscular dystrophy.
  • Symptoms get worse or new symptoms develop, particularly fever with cough or breathing problems.

 

Prevention

 

People with a family history of the disorder may want to seek genetic counseling. Genetic studies done during pregnancy are very accurate in detecting Duchenne muscular dystrophy.

 

 

Open References

References

Muscular Dystrophy Association. www.mda.org/disease/duchenne-muscular-dystrophy . Accessed January 21, 2016.

Sarnat HB. Muscular dystrophies. In: Kliegman RM, Stanton BF, St Geme JW III, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 609.

Warner WC, Sawyer JR. Neuromuscular disorders. In: Canale ST, Beaty JH, eds. Campbell's Operative Orthopaedics. 12th ed. Philadelphia, PA: Elsevier Mosby; 2013:chap 35.

 
  • X-linked recessive genetic defects - how boys are affected

    X-linked recessive genetic defects - how boys are affected - illustration

    There are several X-linked (or sex-linked) recessive genetic disorders, (hemophilia, muscular dystrophy) which are inherited through a genetic defect on an X chromosome. A female has 2 X chromosomes, one she inherited from her mother and one she got from her father. A male has an X chromosome from his mother and a Y chromosome from his father. Since male offspring receive their X chromosome from their mothers, the inheritance of a defect attached to that one copy of the X will cause the disorder.

    X-linked recessive genetic defects - how boys are affected

    illustration

  • X-linked recessive genetic defects

    X-linked recessive genetic defects - illustration

    There are several X-linked (or sex-linked) recessive genetic disorders, (hemophilia, muscular dystrophy) which are inherited through a genetic defect on an X chromosome. A female has 2 X chromosomes, one she inherited from her mother and one she got from her father. A male has an X chromosome from his mother and a Y chromosome from his father. If a woman has the defect on one of her X chromosomes, and the father's X chromosome is normal, there is a 25% chance for each pregnancy to produce: an unaffected girl; a girl who carries the defect; an unaffected boy; or a boy with the disorder.

    X-linked recessive genetic defects

    illustration

    • X-linked recessive genetic defects - how boys are affected

      X-linked recessive genetic defects - how boys are affected - illustration

      There are several X-linked (or sex-linked) recessive genetic disorders, (hemophilia, muscular dystrophy) which are inherited through a genetic defect on an X chromosome. A female has 2 X chromosomes, one she inherited from her mother and one she got from her father. A male has an X chromosome from his mother and a Y chromosome from his father. Since male offspring receive their X chromosome from their mothers, the inheritance of a defect attached to that one copy of the X will cause the disorder.

      X-linked recessive genetic defects - how boys are affected

      illustration

    • X-linked recessive genetic defects

      X-linked recessive genetic defects - illustration

      There are several X-linked (or sex-linked) recessive genetic disorders, (hemophilia, muscular dystrophy) which are inherited through a genetic defect on an X chromosome. A female has 2 X chromosomes, one she inherited from her mother and one she got from her father. A male has an X chromosome from his mother and a Y chromosome from his father. If a woman has the defect on one of her X chromosomes, and the father's X chromosome is normal, there is a 25% chance for each pregnancy to produce: an unaffected girl; a girl who carries the defect; an unaffected boy; or a boy with the disorder.

      X-linked recessive genetic defects

      illustration

    A Closer Look

     

    Tests for Duchenne muscular dystrophy

     
     

    Review Date: 1/5/2016

    Reviewed By: Joseph V. Campellone, MD, Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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