Picture of Dermatomyositis
Dermatomyositis. Dermatomyositis is a rare autoimmune disease that is characterized by a distinctive red or purplish rash as well as muscle weakness. It usually shows up where muscles are used to straighten joints like knuckles, elbows, knees, toes or even eyelids. Hard painful lumps can occur, most often in children.
Text Source: John Hopkins Medicine
National Organization for Rare Disorders