Polymyositis (cont.)

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What causes polymyositis?

To date, no cause of polymyositis has been isolated by scientific researchers. There are indicators of heredity (genetic) susceptibility that can be found in some patients. There is indirect evidence of infection by a virus that has yet to be identified in a muscle disease related to polymyositis that is particularly resistant to treatment, called inclusion body myositis. The pathologist, a physician specialist who interprets the microscope findings of muscle tissue, diagnoses this muscle disease. The muscle tissue in inclusion body myositis displays clear areas within the muscle cells (called vacuoles) when viewed under the magnification of a microscope.

Researchers from Sweden at the national meeting of the American College of Rheumatology in 2007 reported their findings that T-cells of the immune system in some polymyositis or dermatomyositis patients reacted against cytomegalovirus (CMV) and that detectable antibodies against CMV were present. Their conclusion was that there may be subsets of patients who develop their disease, in part, because of infection with this particular virus.

Aside from diseases with which polymyositis can be associated (as mentioned above), many other diseases and conditions can mimic polymyositis. These include nerve-muscle diseases (such as muscular dystrophies), drug toxins (such as alcohol, cocaine, steroids, colchicine, hydroxychloroquine, and cholesterol-lowering drugs, called statins), metabolic disorders (where muscle cells are unable to process chemicals normally), hormone disorders (such as abnormal thyroid), inclusion body myositis, calcium and magnesium conditions, and infectious diseases (such as influenza virus, AIDS, streptococcus and Lyme bacteria, pork tapeworm, and schistosomiasis).

Medically Reviewed by a Doctor on 12/20/2013

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