Dermatomyositis (DM): DM is a distinctive entity identified by a characteristic rash accompanying, or more often preceding, muscle weakness. The rash may consist of a blue-purple discoloration on the upper eyelids with edema (heliotrope rash). A flat red rash on the face and upper trunk, and erythema of the knuckles with a raised violaceous scaly eruption (Gottron's sign). The erythematous rash can also occur on other body surfaces, including the knees, elbows, malleoli, neck and anterior chest (often in a V sign), or back and shoulders (shawl sign), and may worsen after sun exposure. The lateral and palmar areas of the fingers may become rough and cracked, with irregular, "diy" horizontal lines, resembling mechanic's hands. Ref: Dalakas M.C. (2012). Chapter 388. Polymyositis, Dermatomyositis, and Inclusion Body Myositis. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.