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Dermatomyositis by Ricker Polsdorfer, MD

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:

Electromyogram (EMG) —to test muscle activity
Muscle biopsy —to take a sample of muscle tissue
Magnetic resonance imaging (MRI) or ultrasound—to detect inflammation in your muscles.

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

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 RESOUCRES:

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.

Last reviewed November 2012 by Michael Woods, MD

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