How Many Types Of Myositis Are There?
How Many Types Of Myositis Are There? Myositis refers to any condition that causes muscle inflammation. Polymyositis and dermatomyositis are the two of the most common types. Polymyositis causes muscle weakness in both sides of the body, usually in the hips, thighs, shoulders, upper arms and neck. What is the most common type of myositis?