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Dermatomyositis

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(Idiopathic Inflammatory Myopathy)

Definition

Dermatomyositis is an inflammation of muscle and skin.

Causes

The exact cause of dermatomyositis is not known. It may be an autoimmune disorder. The immune system identifies and attacks viruses and bad bacteria in your body. An autoimmune disorder means the immune system begins to attack normal healthy tissue.
A viral infection may trigger the onset of dermatomyositis.

Risk Factors

Your chance of developing dermatomyositis is higher if you have a connective tissue disorder such as:

Symptoms

Dermatomyositis may cause:
  • Skin changes such as:
    • Violet-colored, bumpy, or scaly skin rash (especially around the eyes, upper back, elbows, or knuckles)
    • Itching, especially the scalp
    • Sensitivity to sunlight
    • Calcium deposits
  • Muscle problems such as:
    • Weakness especially in hips, thighs, arms or neck
    • Aching pain in legs, shoulder, arm, or neck
    • Tender muscles
    • Difficulty swallowing and speaking
  • Aching and color changes (red, white, and blue) in fingers, especially in cold temperatures
  • Joint pain
  • Shortness of breath

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. You may be referred to a specialist for further evaluation.
Blood tests may be done to look for infections or signs of muscle damage and inflammation. Your doctor may also do a series of tests on the muscle including:
Other tests that may be done to help rule out other conditions or complications include:
  • Skin biopsy—to take a sample of skin tissue
  • Cancer tests—dermatomyositis is associated with cancer about 15% of the time
  • CAT scan (CT) —to look for any lung involvement
Skin Biopsy
Skin proceedure
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Treatment

There is no cure for dermatomyositis. Treatment is focused on managing the symptoms. Talk with your doctor about the best treatment plan for you. Treatment options include the following:

Physical Therapy

You may be referred to a physical therapist. The therapist will help improve or prevent the loss of muscle strength and function. It may include:
  • Strength and flexibility exercises
  • Guidelines for a general exercise program
  • Tips to modify day to day activities if muscle weakness is interfering

Medication

Corticosteroids can suppress your immune system. This will decrease inflammation in the muscle. Steroid medication can also be used on the skin to relieve skin symptoms. Corticosteroids can cause problems, like lower bone density. To lower this effect your doctor will use the lowest dose needed to control your symptoms. You may also be asked to take supplement like calcium and vitamin D to improve your bone strength.
There are other medication options that can help to suppress the immune system. They may be used with or instead of the corticosteroids.

Intravenous Immune Globulin

Immune globulin has healthy antibodies from several donors. These antibodies can block the unhealthy antibodies associated with dermatomyositis. It is given through an IV.
The infusion needs to be repeated every few weeks.

Lifestyle Changes

Regular exercise can help you develop and maintain muscle strength. Modify the program as needed to prevent irritating your condition. Check with your doctor and physical therapist for exercise guidelines. Rest when needed.
Your skin may also be more sensitive to the sun. Use sunscreen or cover your skin with clothes or a hat.

Prevention

There are no known ways to prevent dermatomyositis.

RESOURCES

American Academy of Family Physicians http://www.familydoctor.org/

The Myositis Association http://www.myositis.org/

National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov/

CANADIAN RESOURCES

The Arthritis Society http://www.arthritis.ca/

Muscular Dystrophy Canada http://www.muscle.ca/

References

Berkow R, Beers MH, Burs M, eds. The Merck Manual . 17th ed. West Point, PA: Merck & Co; 1999.

Bolognia JL, Jorizzo J, Rapini RP. Dermatology . London: Elsevier Science; 2003.

Chung L, Genovese MC, Fiorentino DF. A pilot trial of rituximab in the treatment of patients with dermatomyositis. Arch Dermatol . 2007;143:763-767.

Dalakas MC. Polymyositis, dermatomyositis, and inclusion body myositis. In: Kasper DL, et al, eds. Harrison's Principles of Internal Medicine . 16th ed. New York: McGraw-Hill; 2005: 2540-2545.

Dermatomyositis. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/dermatomyositis/dermatomyositis.htm . Updated August 26, 2012. Accessed October 31, 2012.

Idiopathic inflammatory myopathy. EBSCO Dynamed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated January 3, 2012. Accessed October 31, 2012.

Dold S, Justiniano ME, Marquez J, Espinoza LR. Treatment of early and refractory dermatomyositis with infliximab: a report of two cases. Clin Rheumatol . 2007;26:1186-1188.

Wong EH, Hui AC, Griffith JF, et al. MRI in biopsy-negative dermatomyositis. Neurology . 2005;64:750.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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