Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle. There are many different kinds of muscular dystrophy. Symptoms of the most common variety begin in childhood, mostly in boys. Other types don't surface until adulthood. There's no cure for muscular dystrophy. But medications and therapy can help manage symptoms and slow the course of the disease. The main sign of muscular dystrophy is progressive muscle weakness. Specific signs and symptoms begin at different ages and in different muscle groups, depending on the type of muscular dystrophy.