Causes

The cause of dermatomyositis is unknown. Experts think it may be due to a viral infection of the muscles or a problem with the body's immune system. It can also sometimes occur in patients who have cancer of the abdomen, lung or other body area.

Anyone can develop dermatomyositis, but it most commonly occurs in children age 5 - 15 and adults age 40 - 60. Women develop this condition more often than men do.

Polymyositis is a similar condition, but the symptoms occur without a skin rash.

Symptoms

• Difficulty swallowing
• Muscle weakness, stiffness, or soreness
• Purple or violet colored upper eyelids
• Purple-red skin rash
• Shortness of breath

The muscle weakness may appear suddenly or develop slowly over weeks or months. You may have difficulty raising your arms over your head, rising from a sitting position, and climbing stairs.

The rash may appear over the face, knuckles, neck, shoulders, upper chest, and back.

Exams and Tests

The doctor will perform a physical exam. Tests may include:

• Bloods test to check levels of creatine phosphokinase and aldolase
• ECG
• Electromyography
• Magnetic resonance imaging (MRI)
• Muscle biopsy

Treatment

The disease is treated with anti-inflammatory medicines called corticosteroids and drugs that suppress the immune system.

When your muscle strength gets better, your doctor may tell you to slowly cut back on your doses. However, most people with this condition must take a medicine called prednisone indefinitely.

If the condition is associated with a tumor, the muscle weakness and rash may improve when the tumor is removed.

Outlook (Prognosis)

Some people may recover and have symptoms completely disappear. Doctors have reported several such cases, especially in children.

In adults, death may result from severe and prolonged muscle weakness, malnutrition, pneumonia, or lung failure. The major causes of death are cancer (malignancy) and lung disease.

Possible Complications

• Acute renal failure
• Cancer (malignancy)
• Inflammation of the heart
• Joint pain
• Lung disease

When to Contact a Medical Professional

Call for an appointment with your health care provider if you have muscle weakness or other symptoms of this condition.

References

Goldman L, Ausiello D. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007.

Update Date: 2/8/2012

Reviewed by: Richard J. Moskowitz, MD, Dermatologist in Private Practice, Mineola, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.