Dermatomyositis is inflammation of the skin and underlying muscle tissue that characteristically causes a skin rash and muscle weakness. In most cases, the first symptom is a distinctive skin rash on the face, chest, hands or elbows. The rash is patchy and usually a bluish-purple color. The muscle weakness usually starts in your neck, arms, or hips, and it gets worse over time. The muscle weakness can be felt on both sides of your body and tends to develop in muscles closest to the center of your body.
Dermatomyositis (DM) is an autoimmune disease and a systemic disorder, and people with DM may experience the following complications and disease associations:
- Cancer, particularly cancer of the lungs, ovaries, breast and colon
- Interstitial lung disease
- Swallowing difficulties
- Arthritis
- Heart abnormalities
The exact cause of dermatomyositis is unknown. In a healthy body, cells of immune system attack only foreign or defective cells in the body to protect it from disease. In an autoimmune disease, the immune system attacks normal body cells. In the case of Dermatomyositis (DM), immune system cells attack healthy cells of small blood vessels in the muscle and skin. Over time, this causes muscle fiber to shrink and sometimes cuts off blood supply to the muscle.