- A chronic inflammatory disease of muscle that begins when white blood cells, the immune cells of inflammation, spontaneously invade muscles, especially the muscles closest to the trunk or torso, resulting in sometimes severe muscle pain, tenderness and weakness. There are commonly periods of increased symptoms, called flares or relapses, and periods of decreased symptoms, known as remissions. The disease is slightly more common in females than males. It affects all age groups, although its onset is most common in middle childhood and in the twenties. It occurs throughout the world. It can be associated with skin rash and is then referred to as "dermatomyositis." It also can affect other areas of the body and is, therefore, a systemic illness. Occasionally, polymyositis is associated with other diseases of connective tissue such as systemic lupus erythematosus, scleroderma, and rheumatoid arthritis. Polymyositis is also associated with modestly increased risk of cancer, including non-Hodgkin lymphoma, lung and bladder cancer. There are many other aspects to this important disease that are beyond the scope of this dictionary entry. For fuller information, please see: Polymyositis (a full article about the disease). FocusOnArthritis.com (site with comprehensive information about polymyositis and other connective tissues diseases).
* * *Inflammation of a number of voluntary muscles simultaneously. [poly- + G. mys, muscle, + -itis, inflammation]
* * *poly·myo·si·tis -.mī-ə-'sīt-əs n inflammation of several muscles at once specif an inflammatory disease of unknown cause that affects muscles and esp. skeletal muscles, is characterized typically by weakness usu. of the proximal muscles (as of the pectoral or pelvic girdles or of the neck), muscle and joint pain, pathological muscle changes (as fiber degeneration or infiltration by lymphocytes), pneumonia, and cardiac abnormalities (as arrhythmia or myocarditis) see DERMATOMYOSITIS
* * *n.a generalized disease of the muscles that may be acute or chronic. It particularly affects the muscles of the shoulder and hip girdles, which are weak and tender to the touch. Microscopic examination of the affected muscles shows diffuse inflammatory changes, and relief of the symptoms is obtained with corticosteroid drugs. The skin may be reddened and atrophic. See also dermatomyositis.
* * *poly·myo·si·tis (pol″e-mi″o-siґtis) [poly- + myositis] chronic, progressive myositis with symmetrical weakness of the limb girdles, neck, and pharynx; it can occur in either children or adults. There is usually associated pain and tenderness, and there may be symptoms resembling those of scleroderma, arthritis, systemic lupus erythematosus, or SjÑ†gren syndrome. It is also sometimes associated with malignancy, and may be accompanied by characteristic skin lesions (see dermatomyositis).
Medical dictionary. 2011.