A 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 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.