Muscular dystrophy (DISS-tro-fee) is the umbrella term to describe more than 40 diseases affecting primarily skeletal muscles.Some forms first become apparent in infancy or childhood, but others don't appear until later. The distribution and amount of the affliction depend on the type of dystrophy. The diseases are generally inherited, although not always; they involve progressive muscle weakness, and they're most commonly found in males. They differ in severity, depending on the age they first appear, the muscles affected, the rate at which symptoms progress (pro-GRESS), and the way they're inherited. These diseases include motor neuron (NEW-ron) diseases, diseases of the neuromuscular junction, and diseases of peripheral nerves. One disease you may have heard of is A-L-S, also known as Lou Gehrig's (GEH-rigg's) disease. Researchers have identified genes for nearly all the disorders, which makes it more likely to make an accurate diagnosis, as well as lead to developing treatments. Some of the disorders are nongenetic and are caused by misdirected activity of the body's immune system. Researchers are working on ways to change the immune system's actions to compensate for these activities. There's no cure, but symptoms can be treated with exercise programs, physical therapy, and rehabilitative (re-huh-BILL-uh-tay-tiv) devices. With improved medical care, especially with problems involving the heart and lungs, children with muscular dystrophy are living longer than ever before.