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Causes
By Mayo Clinic staff
Polymyositis is in a group of diseases or disorders of the muscles called inflammatory myopathies. The cause of most inflammatory myopathies is unknown.
Infections caused by bacteria, parasites or viruses can cause inflammatory myopathies, but in most cases of polymyositis, doctors aren't able to identify a preceding infection. Some doctors think certain people may have a genetic susceptibility to the disease.
Inflammatory myopathies share many characteristics with autoimmune disorders, in which your immune system attacks normal body components. Normally, your immune system works to protect your healthy cells from attacks by foreign substances, such as bacteria and viruses. If you have polymyositis, an unknown cause may act as a trigger for your immune system to begin producing autoimmune antibodies (autoantibodies) that attack your body's own tissues.
Many people with polymyositis show a detectable level of autoantibodies in their blood.
- NINDS polymyositis information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/polymyositis/polymyositis.htm. Accessed May 21, 2009.
- Baer A. Advances in the therapy of idiopathic inflammatory myopathies. Current Opinion in Rheumatology. 2006;18:236.
- Dalakas MC. Inflammatory disorders of muscle: Progress in polymyositis, dermatomyositis and inclusion body myositis. Current Opinion in Neurology. 2004;17:561.
- Miller ML. Clinical manifestations and diagnosis of adult dermatomyositis and polymyositis. http://www.uptodate.com/home/index.html. Accessed May 8, 2009.
- Di Martino SJ, et al. Newer therapeutic approaches: Inflammatory muscle disorders. Rheumatic Disease Clinics of North America. 2006;32:121.
- Koski CL, et al. Intravenous immunoglobulin use for neurologic diseases. Journal of Infusion Nursing. 2006;29:S21.
- Amato AA, et al. Treatment of idiopathic inflammatory myopathies. Current Opinion in Neurology. 2003;16:569.
- Oddis CV. Current approach to the treatment of polymyositis and dermatomyositis. Current Opinion in Rheumatology. 2000;12:492.
- Walker UA. Imaging tools for the clinical assessment of idiopathic inflammatory myositis. Current Opinion in Rheumatology. 2008;20:656.
- Miller ML, et al. Initial treatment of dermatomyositis and polymyositis in adults. http://www.uptodate.com/home/index.html. Accessed May 8, 2009.
- Miller ML, et al. Treatment of recurrent and resistant polymyositis and dermatomyositis. http://www.uptodate.com/home/index.html. Accessed June 15, 2009.
