Dermatomyositis (dur-muh-toe-my-uh-SY-tis) is an uncommon inflammatory disease marked by muscle weakness and a distinctive skin rash. The condition can affect adults and children. In adults, dermatomyositis usually occurs from the late 40s to early 60s. In children, it most often appears between 5 and 15 years of age. Dermatomyositis is a connective-tissue sickness associated with myositis that is characterised by inflammation of the muscles and also the skin. However myositis most often affects the skin and muscles. It is a general disorder that affects the joints, the musculature, the lungs, and also the heart. The main symptoms include skin rash and symmetric proximal muscle weakness which may be accompanied by pain. Dermatomyositis is a rare inflammatory autoimmune disease which affects muscles.