Autoimmune Myopathies

What is it?

Autoimmune myopathies are a group of diseases that involve inflammation of the muscles and may be associated with diseases of internal organs. Diseases affecting muscles include polymyositis, dermatomyositis and inclusion body myositis. The main symptom is muscle weakness in the upper arms, upper legs and neck, muscle pain, fatigue, joint pain and swelling, rashes over the face and knuckles, fevers, swallowing difficulty and shortness of breath.

What causes it?

The cause of myopathies is unknown, but environmental factors (such as viral infections) and genetic predisposition are felt to be important in some cases.

Who gets it?

Only about 1 new case per 100,000 is diagnosed each year.

Myopathies occur two to three times more frequently in women than men.

Severity of disease varies from a mild form with almost no symptoms to a severe, life-threatening disease.

How is it diagnosed?

Diagnosis is attained through a history and physical exam, certain laboratory tests, muscle biopsy and electromyography (a study of the electrical activity of muscle). Other diseases or conditions such as hypothyroidism, toxin exposure, drug reactions and genetic disorders may also affect muscles and need to be ruled out.

In the case of dermatomyositis, its high association with cancer warrants a thorough workup to exclude an underlying malignancy.

How is it treated?

These complex diseases can affect many body organs other than muscles and skin, with lung and gut involvement signifying particularly severe manifestations of the disease. While not curable, many of the symptoms can be treated effectively with patient education, physical and occupational therapy, and medications. Medications may include corticosteroids and immuno-suppressive drugs (drugs that keep the immune system from attacking its own body), such as methotrexate, azathioprine and cyclophosphamide. For patients whose disease was diagnosed late, or the muscule damage was severe, a prolonged period of rehabilitation and muscular re-conditioning may be necessary. For those with swallowing difficulties, a period of supplementary nasogastric feeding may be required to prevent aspiration of food into the lungs as well as to ensure adequate nutrition.

For More Information

If you want more information on this or any other form of arthritis, visit the Arthritis Foundation website at www.arthritis.org. For more information about myositis and myopathies, please visit the Myositis Association of America's Web site at www.myositis.org