What is Dermatomyositis?

Dermatomyositis is one of a group of muscle diseases known as the inflammatory myopathies, which are characterized by chronic muscle inflammation accompanied by muscle weakness.Dermatomyositis’ cardinal symptom is a skin rash that precedes or accompanies progressive muscle weakness.  The rash looks patchy, with bluish-purple or red discolorations, and characteristically develops on the eyelids and on muscles used to extend or straighten joints, including knuckles, elbows, heels, and toes.  Red rashes may also occur on the face, neck, shoulders, upper chest, back, and other locations, and there may be swelling in the affected areas.  The rash sometimes occurs without obvious muscle involvement.  Adults with dermatomyositis may experience weight loss or a low-grade fever, have inflamed lungs, and be sensitive to light.  Children and adults with dermatomyositis may develop calcium deposits, which appear as hard bumps under the skin or in the muscle (called calcinosis).  Calcinosis most often occurs 1-3 years after the disease begins.  These deposits are seen more often in children with dermatomyositis than in adults.  In some cases of dermatomyositis, distal muscles (muscles located away from the trunk of the body, such as those in the forearms and around the ankles and wrists) may be affected as the disease progresses.  Dermatomyositis may be associated with collagen-vascular or autoimmune diseases, such as lupus.