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Muscular Dystrophy

Fact Sheet

What is Muscular Dystrophy?

Muscular Dystrophy is a term that refers to a group of muscle disorders in which the face, arm, leg, spine, or heart muscles gradually shrink and weaken over time. There are a variety of different types of Muscular Dystrophy, including Duchenne Muscular Dystrophy, Myotonic Dystrophy, Becker’s Muscular Dystrophy, Facioscapulohumeral muscular dystrophy, the limb-girdle muscular dystrophies, and the Mitochondrial Myopathies. The different types are distinguished by factors such as the:

  • age at which symptoms usually start
  • pattern of muscle weakness
  • speed at which the disease progresses
  • involvement of other tissues besides muscle
  • pattern of inheritance

Muscular dystrophy is rare. For example, although Duchenne muscular dystrophy is one of the more common types, it occurs in only 1 out of every 50,000. The other types of muscular dystrophy are even more rare.

How is it manifested?

All Muscular Dystrophies are inherited. Each type of Muscular Dystrophy is associated with a distinct genetic mutation. The nature of the gene mutation and which chromosome it is located on determine the characteristics of the Muscular Dystrophy and the way the disease is passed from one generation to the next.

The symptoms and age of onset depend on the type of muscular dystrophy. Symptoms of muscular dystrophy often include:

  • problems with coordination and mobility with frequent falls
  • muscle weakness
  • joint stiffness

Duchenne muscular dystrophy symptoms appear early, usually between the ages of three and five, or earlier. The condition progresses quickly, with many people needing a wheelchair by the age of 12. Symptoms include those listed above, plus problems with the bones in the back and chest, as well as fatigue. Those with the condition may eventually have trouble breathing and develop pneumonia. This diagnosis can be associated with delays in other areas of development.

Becker’s muscular dystrophy symptoms typically start to appear between the ages of five and fifteen and are much less severe than Duchenne Muscular Dystrophy symptoms. As well as the symptoms listed above, heart disease, problems with the curvature of the spine, fatigue, problems with thinking, and breathing difficulties can occur.

Facioscapulohumeral muscular dystrophy also called Landouzy-Dejerine Muscular Dystrophy has symptoms that include weak facial and shoulder muscles and difficulty with lifting arms, whistling, and closing eyes. It affects mainly the upper body and can also cause hearing loss, speech problems, and changes in heart rhythm. Symptoms often start in the teen years, but may also start at a later stage.

Limb-girdle muscular dystrophies affect the muscles that are closest to the body (shoulder, upper arm, pelvis, and thigh muscles). Symptoms usually start to appear in childhood or early adulthood. The heart and breathing muscles may sometimes be affected.

Mitochondrial myopathies are caused by defects in the genes of the mitochondria, which are specialized units found inside cells that create the energy needed for cells to work. Symptoms include those listed above, plus heart problems, seizures, and problems with vision and hearing.

Myotonic muscular dystrophy is the most common form of adult onset, but can affect people at any age. It is diagnosed by the time individuals reach their late twenties. This type of Muscular Dystrophy can also affect the heart, eyes (cataracts), lungs, digestive tract, and brain function and can be associated with diabetes.

There is, however, a distinct difference between the type that affects newborn infants — Congenital MMD — and the type that begins in adolescence or adulthood — adult-onset MMD.

Infants with congenital MMD have severe muscle weakness, including weakening of the muscles that control breathing and swallowing. These problems can be life threatening and need intensive care.

How is it diagnosed or detected?

In diagnosing any form of Muscular Dystrophy, a doctor usually begins by taking a patient and family history and performing a physical examination. Much can be learned from these steps, including the pattern of weakness. The history and physical go a long way toward making the diagnosis, even before any complicated diagnostic tests are done. Further testing may include a muscle biopsy, DNA testing, blood enzyme tests and electromyography (EMG).

The doctor also wants to determine whether the patient’s weakness results from a problem in the muscles themselves or in the nerves that control them. Problems with muscle-controlling nerves, or motor nerves, originating in the spinal cord and reaching out to all the muscles, can cause weakness that looks like a muscle problem but really is not.

Usually, the origin of the weakness can be pinpointed by a physical exam. Occasionally, special tests called nerve conduction studies and EMG are done. In these tests, electricity and very fine pins are used to stimulate and assess the muscles or nerves individually to see where the problem lies. Electromyography is uncomfortable but not usually very painful.

Who is affected?

MD occurs worldwide and affects all races. Its incidence varies, as some forms are more common than others. The most common forms in children, Duchenne and Becker Muscular Dystrophy, affect approximately 1 in every 3,500 -5,000 boys, or between 400 and 600 live male births each year (United Stated source).

Additional Resources:

Muscular Dystrophy
National Office:
Muscular Dystrophy Canada
2345 Yonge St, Suite 900
Toronto, Ontario M4P 2E5
Telephone: 1-866-MUSCLE-8

Muscular Dystrophy Canada’s dedicated volunteers and staff across the country raise funds and work hard to support the independence and full participation of Canadians with neuromuscular disorders, fund research to find a cure and improve the quality of life of people with neuromuscular disorders, assist our clients to participate in the decisions that affect them, and collaborate with others for social change.

Books and Literature:

Muscular Dystrophy in Children: A Guide for Families (ISBN-13: 978-1888799330)
Author: Irwin M. Siegel
This book covers everything from available medical treatments to helping the child grow up with a positive self-image to what the future holds for the treatment of muscular dystrophy and more.

Muscular Dystrophy: The Facts (ISBN-13: 978-0192632173)
Author: Alan Emery
Written specifically for people with muscular dystrophy and their families, this new edition of Muscular dystrophy: the facts answers many of the questions asked about how and why it occurs, and how it will affect the life of a recently diagnosed child. Throughout, the different types of muscular dystrophy are described with a minimum of technical jargon.

The content contained in this document is for general information purposes. It is not intended to diagnose or treat a child.

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