Muscular dystrophy (MD) is a genetic disorder that gradually weakens the body’s muscles. It’s caused by incorrect or missing genetic information that prevents the body from making the proteins needed to build and maintain healthy muscles. A child who is diagnosed with MD gradually loses the ability to do things like walk, sit upright, breathe easily, and move the arms and hands. This increasing weakness can lead to other health problems. There are several major forms of muscular dystrophy, which can affect the muscles to varying degrees. In some cases, MD starts causing muscle problems in infancy; in others, symptoms don’t appear until adulthood.