Many people don't know much about muscular dystrophy. Yet a quarter of a million kids and adults are living with the disease, so chances are you may know someone who has it. Muscular dystrophy (MD) is a group of rare diseases. It is a genetic disorder that weakens the muscles that help the body move. They cause muscle fibers to weaken and break down. People with MD have incorrect or missing information in their genes, which prevents them from making the proteins they need for healthy muscles. MD affects the skeletal or voluntary muscles that control movement in the arms, legs and trunk. It also can affect the heart and other involuntary muscles. These disorders vary in their age of onset, in severity and in the pattern of which muscles are affected. All forms of muscular dystrophy, however, grow worse as muscles progressively degenerate. In some types of muscular dystrophy, the heart, the gastrointestinal system, endocrine glands, the skin, the eyes and other organs may be affected. MD weakens muscles over time, so children, teens, and adults who have the disease can gradually lose the ability to do things like walking or sitting up.

MD is a sex-linked recessive disease. It typically passes from a mother (who has no symptoms) to her son. Because MD is genetic, people are born with the problem - it's not contagious and you can't catch it from someone who has it. MD passes from parent to child (genetic) and gets worse over time (progressive). All of the muscular dystrophies are genetic disorders, although the types of inheritance vary, and Duchenne muscular dystrophy, the most common and best known of the childhood muscular dystrophies, often arises from new mutations.