Dermatomyositis is an autoimmune muscle disease that involves inflammation and a skin rash. It is a type of inflammatory myopathy. The cause of dermatomyositis is unknown. Experts think it may be due to a viral infection of the muscles or a problem with the body’s immune system. It may also occur in patients who have cancer in the abdomen, lung, or other parts of the body. Anyone can develop dermatomyositis. It most commonly occurs in children age 5 – 15 and adults age 40 – 60. Women develop this condition more often than men. Symptoms may include: problems swallowing, muscle weakness, stiffness, or soreness, purple color to the upper eyelids, purple-red skin rash, and shortness of breath. The muscle weakness may come on suddenly or develop slowly over weeks or months. You may have trouble raising your arms over your head, getting up from a sitting position, and climbing stairs. The rash may appear on your face, knuckles, neck, shoulders, upper chest, and back. Symptoms may go away completely in some people, such as children. The condition may be fatal in adults due to severe muscle weakness, malnutrition, pneumonia, or lung failure. The major causes of death with this condition are cancer and lung disease.