Dermatomyositis (DM) affects people of any age or sex, but is found in more women than men.  Dermatomyositis is becoming more prevalent in African-American women for reasons that are poorly understood.

DM is the easiest type of myositis to diagnose because of the skin rash which is often seen before any muscle weakness is felt. The DM rash looks patchy, dusky, and reddish or purple. It is found on the eyelids, cheeks, nose, back, upper chest, elbows, knees and knuckles. Some people also have hardened bumps under the skin, called calcinosis. The skin rash and weak muscles are caused by inflammation, or swelling, in the blood vessels under the skin and in the muscles, also called vasculitis. Patients who have the skin rash but feel no muscle weakness have amyopathic DM, or DM sine myositis.

The weakness begins with muscles that are closest to and within the trunk of the body. Neck, hip, back and shoulder muscles are examples. Some DM patients have muscle pain.

Signs and symptoms:

  • Rash on the eyelids, cheeks, nose, back, upper chest, elbows, knees, and knuckles
  • Scaly, dry, or rough skin
  • Trouble rising from a seated position or getting up after a fall
  • General tiredness
  • Inflamed or swollen areas around fingernails
  • Sudden or progressive weakness in muscles in neck, hip, back, and shoulder muscles
  • Difficulty swallowing (dysphagia) or a feeling of choking
  • Hardened lumps or sheets of calcium (calcinosis) under the skin