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Home Science Areas of Focus Rare Disease Duchenne Muscular Dystrophy

Striving for Better Patient Outcomes

Duchenne muscular dystrophy, one of the various forms of muscular dystrophy, is a rare genetic disease that affects boys almost exclusively and causes progressive weakness.1 Patients typically lose the ability to walk when they reach 8 to 12 years of age, and die as a result of respiratory or cardiac failure.1 Before treatments were available, children with the disease typically died in their teens.2 As a result of steroid use and supportive respiratory therapies, they now live well into their 20s,3 but more must be done to allow these patients to live a fuller life.

This condition is a priority for Pfizer, and our researchers are developing an investigational gene therapy that is currently being evaluated in a clinical trial. In addition, several companies are working on treatments using gene therapy and gene repair.

  • Duchenne muscular dystrophy is a genetic disease caused by a mutation in the gene for dystrophin. The muscle cells of children with this condition do not produce enough dystrophin, a protein that helps protect muscle cells from the stresses associated with normal movement. As the disease progresses, muscles become damaged and are slowly replaced with fat and connective tissue. Eventually, the muscles become so weak and scarred that they are unusable.1

  • The defective gene that causes Duchenne muscular dystrophy can be inherited in families, but it also occurs in people whose families do not have a history of the condition. Because the gene is located on the X chromosome, the disease affects mostly boys. Girls can have it too, although it is extremely rare. Females can be carriers of the altered gene without having the disease and have a 50% chance of passing the gene to their children. Duchenne muscular dystrophy affects less than one in 3,500 male infants worldwide.1

  • Children born with this condition typically show the first signs of muscle weakness before the age of six. Muscle weakness typically affects the hips, pelvic area, and thighs first, usually causing difficulty with standing and walking. Additional early signs and symptoms include:4

    • Developmental delay
    • Muscle weakness
    • Clumsiness
    • Waddling gait
    • Difficulty or inability to perform activities such as climbing stairs, running, and/or jumping
    • Enlarged calf muscles
    • Poor standing posture
    • Learning difficulties

    Later, the arms, lower legs, and trunk become weak as well. By age 12, many children can no longer walk independently and need to use a wheelchair to get around.1 By the early teens, the heart and respiratory muscles are also affected. Difficulties breathing or with the heart are the usual causes of death. Tragically, few individuals with this disease today live beyond their 20s.5

  • Children are usually diagnosed with the disease between the ages of 1 and 6.6 The diagnosis is made after a thorough evaluation and testing by a healthcare team. Often a patient is referred to a neurologist or a specialist in neuromuscular diseases for diagnosis. In addition to a careful examination and a full history, including the identification of any known relatives with a similar condition, several tests may be ordered to help make the diagnosis.4 These include:4

    • A blood test for creatine kinase, a protein whose levels increase in the blood as a result of muscle damage
    • A muscle biopsy, in which a small sample of muscle is taken to look for dystrophin
    • A genetic test to determine whether the dystrophin gene has a mutation
  • There are no treatments available that can stop or reverse the basic disease process in Duchenne muscular dystrophy. The only medications that have been shown to slow the course of the disease are corticosteroids, such as prednisone.4 Other therapies aim to ease the symptoms of the disease and improve the patients' quality of life. Medicines can also be given to improve heart function. Physical therapy is used to promote mobility. Assisted breathing devices are also often used, especially at night. Surgery is sometimes helpful in cases where the patient has scoliosis and experiences muscle pain.7

Duchenne Muscular Dystrophy is a focus of our Rare Disease Therapeutic Area.

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