Definition of Polymyositis – adult
Polymyositis is a relatively uncommon inflammatory disease that leads to significant muscle weakness.
Causes, incidence, and risk factors
Polymyositis is a skeletal muscle disease also known as idiopathic inflammatory myopathy. The cause of this disorder is unknown. It is thought that an autoimmune reaction or a viral infection of the skeletal muscle may cause the disease.
Polymyositis is a systemic disease, which means it affects the whole body. Symptoms include:
The disease is treated with corticosteroid medications. When an improvement in muscle strength is achieved, usually in 4 to 6 weeks, the medication is slowly tapered off. Maintenance therapy with prednisone may be continued indefinitely. In people who fail to respond to corticosteroids, medications to suppress the immune system may be used.
Remission (a period when no symptoms are present) and recovery occur in many patients, especially children. For most others, immunosuppressant drugs can control the disease. In adults, death may result from severe and prolonged muscle weakness, malnutrition, pneumonia, or respiratory failure. The major causes of death are cancer (malignancy) and lung disease.
Ariel D. Teitel, MD, MBA, Chief, Division of Rheumatology, St. Vincent’s Hospital, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 2/22/2009