Dermatomyositis (dur-muh-toe-my-uh-SY-tis) is an uncommon disease marked by muscle weakness and a particular rash. The condition can affect adults and youngsters. In adults, dermatomyositis usually occurs from the late 40s to early 60s. In children, it most frequently appears between 5 and 15 years aged. Treatment includes medication or other therapies. In rare cases, surgery could also be wont to remove calcium deposits.