Dermatomyositis is a rare inflammatory disease that causes muscle weakness and a distinctive skin rash. It primarily affects children ages 5 to 15 and adults in their late 40s to early 60s. Women are much more likely than men to develop the disease.

Dermatomyositis is among a group of disorders classified as inflammatory myopathies. It occurs as a result of inflammation in the blood vessels under the skin and in the muscles (vasculitis). As a result, patients experience progressive muscle weakness that begins with muscles closest to and within the trunk of the body.

In addition, patients typically experience a patchy, dusky, reddish or purple rash that affects the face, eyelids and areas around the elbows, knuckles, knees, nails, chest and back.

Scientists do not fully understand the cause of dermatomyositis. It is believed to be caused by an autoimmune disorder, in which the immune system mistakenly attacks the body’s own tissues.

The earlier dermatomyositis is diagnosed, the more effective treatment is likely to be. In addition to performing a physical examination and compiling a medical history, a physician is likely to use one or more of several procedures to test the condition of a patient’s muscle tissue.

There is no cure for dermatomyositis. However, proper treatment can help patients to improve muscle strength and function as well as skin appearance. This may include the use of various medications and other techniques such as physical therapy. Several other treatments for dermatomyositis are now being tested.