Muscular dystrophy (say: mus-kyoo-lur dis-troh-fee) is a disease in which the muscles of the body get weaker and weaker and slowly stop working. Muscles and membranes need many different kinds of proteins to stay healthy. When you hear the word "protein" you might think of food because foods, such as meat and peanut butter, contain protein. But we're talking about another kind of protein — the kind your body actually creates. Your genes tell your body how to make the proteins your muscles need. But in people with MD, these genes have wrong information or leave out important information, so the body can't make these proteins properly.

Without these proteins, the muscles break down and weaken over time. As this happens to muscles, people with MD begin to have problems with the way their bodies work.