Dermatomyositis is a muscle disease that causes inflammation and a skin rash. It is a type of inflammatory myopathy.

The cause is unknown. Experts think it may be due to a viral infection of the muscles or a problem with the body's immune system.

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

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

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

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

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

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

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 persons 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.

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.

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

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

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