Polymyositis and dermatomyositis are problems with your immune system. Polymyositis attacks your muscles. Dermatomyositis attacks your skin and muscles.
These problems affect people in different ways. Most people have muscle weakness. Some people also have swelling or pain. Others get a rash.
Your symptoms depend on the muscles that are affected. It may be hard to swallow if your throat muscles are affected. And if your chest muscles are affected, it could be hard to breathe.
Medicines can help with swelling. They may also help control your immune system. Physical therapy and other exercises can also help.