Dermatomyositis is connective-tissue disease that is characterized by inflammation of the muscles and the skin.

Causes, incidence, and risk factors

The cause of this disorder is unknown. It is theorized that an autoimmune reaction or a viral infection of the skeletal muscle may cause the disease. It can affect people at any age, but most commonly occurs in people 40 to 60 years old, or in children from 5 to 15 years old.

It affects women much more often than men. Muscle weakness may appear suddenly or occur slowly over weeks or months. There may be difficulty with raising the arms over the head, rising from a sitting position, and climbing stairs.

A dusky, purplish red rash may appear over the face, neck, shoulders, upper chest, and back. Joint pain, inflammation of the heart, and lung (pulmonary) disease may occur.

A malignancy may sometimes be associated with this disorder. A similar condition is called polymyositis when the symptoms occur without any skin manifestations.


  • Muscles weak, stiff or sore  
  • Butterfly rash  
  • Upper eyelids purple/violet colored  
  • Muscle weakness  
  • Red, dusky skin rash  
  • Difficulty swallowing  
  • Shortness of breath  
  • Skin redness or inflammation

Signs and tests
During a physical examination, the doctor will identify muscle weakness and the typical rash.

Tests may include:

  • Electromyography, showing inflammation in muscles  
  • Magnetic resonance imaging (MRI)  
  • A muscle biopsy  
  • An elevated serum creatine phosphokinase  
  • An elevated serum aldolase  
  • ECG

The disease is treated with corticosteroid medications or other immunosuppressive drugs. When an improvement of muscle strength is achieved, the medication is slowly tapered. Maintenance therapy with prednisone is often continued indefinitely.

If the condition is associated with a tumor, the condition may improve if the tumor is removed.

Expectations (prognosis)
Remissions and recovery have been reported, especially in children. In adults, death may result from severe and prolonged muscle weakness, malnutrition, pneumonia, or respiratory failure. The outcome is usually worse if cardiac or pulmonary involvement is present.


  • Acute renal failure  
  • Associated malignancy  
  • Cardiac, pulmonary, or abdominal Complications

Calling your health care provider
Call for an appointment with your health care provider if you experience the signs and symptoms of dermatomyositis.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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