Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Muscular Dystrophy

What Is It?

Muscular dystrophy (MD) is a group of disorders that cause the body's muscles to become increasingly weak. Muscular dystrophy is an inherited condition.

Types of muscular dystrophy include:

• Duchenne dystrophy — This is the most severe type of muscular dystrophy. It is also the most common.
  
  In Duchenne dystrophy, the muscles produce abnormally low levels of dystrophin. Dystrophin is a muscle protein. When dystrophin levels are low, the membranes around muscle cells become weak. They tear easily. Eventually, the muscle fibers die.
  
  Duchenne dystrophy primarily affects boys. Women usually do not have symptoms of Duchenne dystrophy. But they can pass it on to their children.

• Becker-type muscular dystrophy — Like Duchenne dystrophy, Becker-type affects dystrophin production and occurs in males. However, the illness is much rarer than Duchenne. And it causes milder symptoms.
  
  Some people have a form of disease that falls in between Duchenne and Becker-type.

• Myotonic dystrophy — Myotonic dystrophy can occur in men and women. It is the most common form of adult MD. Symptoms often start in adolescence.

• Limb-girdle muscular dystrophy — Limb-girdle MD affects muscles of the shoulders and hips. It includes several different illnesses. It can be inherited by both males and females.

• Facioscapulohumeral muscular dystrophy — This form of MD occurs in males and females. Weakness of the facial muscles and the shoulders is typical.
  
  Facioscapulohumeral MD often strikes several members of the same family. However, the symptoms vary in intensity. Family members may have such mild symptoms that they are unaware of any muscle problems.

There are at least two other forms of the illness. These are congenital muscular dystrophy and Emery-Dreifuss dystrophy. Emery-Dreifuss MD causes upper arm and lower leg weakness, and poor heart function. Some forms of congenital muscular dystrophy are associated with decreased mental function.