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Dermatomyositis

Skin symptoms aid in diagnosis

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Updated December 11, 2005

Dermatomyositis is an inflammatory muscle disease (myopathy). It primarily affects the skin and muscles but may affect other organ systems of the body. Research suggests that it is an autoimmune disorder, in which the body attacks its own healthy cells.

Dermatomyositis may occur in people of any age. In adults the peak onset is at about 50 years of age. Known as juvenile dermatomyositis in children, the peak age of onset is 5-10 years old. It affects females twice as often as males, and occurs in people of all ethnic backgrounds.

Symptoms
Dermatomyositis produces symptoms in the skin and muscles such as:

  • A reddish-purple-to-dusky red rash in a symmetrical distribution around the eyes (heliotrope rash)
  • Dark red bumps (Gottron papules) or raised blotches (plaques) over the knuckles, finger or toe joints, elbows, ankles, or knees
  • In children, firm yellow or flesh-colored nodules (calcinosis) may appear over the same bony prominences
  • Some individuals also have a scaly scalp or diffuse hair loss
  • Muscle symptoms include fatigue or weakness when climbing stairs, rising from a sitting position, or lifting the arms.
Although less common, individuals with dermatomyositis may also have systemic symptoms such as arthritis, shortness of breath, or difficulty swallowing or speaking. Adults older than 60 years of age with dermatomyositis seem to have a higher risk of developing cancer.

Diagnosis
Individuals with dermatomyositis often have skin disease as their initial symptoms. The characteristic rash and papules, as well as calcinosis nodules in children, will suggest the diagnosis. Sometimes the skin lesions may be mistaken for those of lupus erythematosus, psoriasis, or lichen planus. Children with dermatomyositis may be hard to diagnose until the characteristic skin symptoms become apparent.

In addition to the skin symptoms, blood tests can be done to detect muscle enzymes and markers of inflammation. Some individuals with dermatomyositis have a positive antinuclear antibody (ANA) blood test. Magnetic resonance imaging (MRI), electromyography (EMG), and muscle biopsy can assess muscle disease and damage.

Treatment
Treatment for dermatomyositis focuses on controlling the muscle disease and skin symptoms. Generally a corticosteroid such as prednisone is administered to decrease muscle inflammation. If the steroid side effects become severe, immunosuppressant or cytotoxic medications, such as methotrexate (Rheumatrex) or azathioprine (Imuran), may be used. Methotrexate may also help reduce the skin symptoms. Individuals with dermatomyositis are photosensitive and should protect their skin from sun exposure.

If muscle weakness is present, physical and occupational therapy may help improve muscle function and prevent complications such as contractures. Some individuals may need treatment for systemic symptoms or complications.

Prognosis
Most individuals with dermatomyositis will require long-term treatment. Calcinosis may complicate the treatment of the disease in children and adolescents. Some individuals may develop cancer or organ failure, leading to a shortened life expectancy. However, many individuals respond well to treatment and have relief of some or all of their symptoms.

Last updated 12/10/05

Information for this article was taken from:
- Callen, J.P. (2002). Dermatomyositis. eMedicine, accessed at http://www.emedicine.com/med/topic2608.htm
- The Myositis Association. What is myositis?

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