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Polymyositis is a systemic connective tissue disorder characterized by inflammatory and degenerative changes in the muscles, leading to symmetric weakness and some degree of muscle atrophy. The areas principally affected are the hip, shoulders, arms, pharynx and neck.
Symptoms of Polymyositis may start gradually or suddenly. The symptoms often wax and wane for no apparent reason.
The major symptom of the disorder is muscle weakness, most often in the hip and shoulder areas, eventually making it difficult for patients to lift their arms or to climb steps. Other muscles which may be affected are the neck and throat muscles, which may result in difficulty in swallowing and cause changes in the voice. Rarely, chest muscles are affected.
The muscle weakness may appear suddenly and progress over weeks to months. The difficulty in swallowing and dilatation of the lower esophagus and small intestine may be indistinguishable from that in scleroderma (progressive systemic sclerosis), (For more information on this disorder, choose "Scleroderma" as your search term in the Rare Disease Database.) The muscles of the hands, feet and face sometimes escape involvement. Muscle pain may occur, especially when grasping an object. Contractures of the limbs may develop late in the chronic stage.
Other symptoms of polymyositis may include fever, weight loss and occasionally pain or tenderness in muscles and joints. A few people with polymyositis have an extreme sensitivity to cold (Raynaud's phenomenon) that is most often felt in the fingers. Raynaud's phenomenon is caused by narrowing of the blood vessels in the fingers. (For more information, choose "Raynaud" as your search term in the Rare Disease Database.) People with polymyositis may develop numb and shiny red areas around and under the finger nails.
Pain in many joints (polyarthralgia), accompanied at times by swelling, fluid and other evidence of non-deforming arthritis, occurs in approximately one third of patients with polymyositis. These rheumatic complaints tend to be mild and respond well to corticosteroids. Gastrointestinal involvement, except for the pharynx and the esophagus, is relatively uncommon in polymyositis.
Inflammation of the lungs with increase of interstitial tissue (interstitial pneumonitis), manifested by difficulty in breathing and by coughing, may precede myositis and dominate the clinical picture.
Involvement of the heart, detected chiefly by irregularities in the electrocardiogram (ECG), has been reported. Acute kidney failure has been reported as a consequence of excess muscle protein myoglobin in the urine (Crush syndrome) due to severe disintegration of muscle (rhabdomyolysis). Sjogren's syndrome can occur in some patients with polymyositis. (For more information, choose "Sjogren" as your search term in the Rare Disease Database.)
Abdominal symptoms, more common in children, may be associated with the passage of dark stools or the vomiting of blood from gastrointestinal ulcerations that may progress to perforation and require surgical intervention.
An associated malignancy, usually a carcinoma, may occur in about 15 percent of males and a smaller proportion of females over age 50 who have polymyositis.
The cause of polymyositis is unknown. The disorders may be caused by the body's natural immune defense mechanisms attacking its own tissue (autoimmune reaction). Viruses may also play a role.
The injection of collagen for cosmetic use has been implicated in the onset of a polymyositis-like syndrome. Injectable bovine collagen has been used to reduce wrinkles and facial scars, usually in women. The onset of polymyositis is suspected to be an autoimmune reaction to the collagen.
Polymyositis may appear at any time from infancy through the age of 80 years, but most commonly they occur between 40 to 60 years. In children, the symptoms usually appear between the ages of five to 15 years. Females are affected twice as often as males.
Symptom of the following disorders can be similar to those of Polymyositis. Comparisons may be useful for a differential diagnosis:
Scleroderma (Progressive Systemic Sclerosis) is a rare, chronic collagen vascular disorder characterized by diffuse hardening, degenerative changes and vascular inflammation of the connective tissues of the skin, joints and many visceral organs. It shares certain clinical findings with polymyositis. (For more information on this disorder, choose "Scleroderma" as your search term in the Rare Disease Database.)
Systemic Lupus Erythematosus (SLE) is an inflammatory connective tissue disorder that can affect many parts of the body including the joints, skin and internal organs. SLE is a disease of the body's immune system. It shares certain clinical findings with Polymyositis. (For more information on this disorder, choose "Lupus" as your search term in the Rare Disease Database.)
Corticosteroids such as prednisone, (together with antacids and potassium supplements), are widely used in treatment of Polymyositis. Measurement of muscle enzyme activity is used to gauge the effectiveness of therapy. Reduction of these enzymes to normal values is noted in a majority of patients with this disorder within 4 to 6 weeks after treatment is started. This is followed by an improvement in muscle strength. At this point the dose of prednisone can usually be reduced slowly. In many cases of adult polymyositis prolonged maintenance therapy with prednisone may be necessary indefinitely.
Immunosuppressive drugs such as methotrexate, cyclophosphamide, chlorambucil and azathioprine have been beneficial to patients who fail to respond to corticosteroids alone. Some patients have received methotrexate for 5 years or longer for control of this disorder.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
A unit of the National Institute of Environmental Health Sciences, called the Environmental Autoimmunity Group (EAG), has been established in Bethesda, MD, at the NIH to conduct pioneering research in understanding the genetic and environmental risk factors that may result in autoimmune disease.
The EAG is currently enrolling families in which an adult or child meets criteria for rheumatoid arthritis/juvenile rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, or myositis and in which a twin or sibling of the same gender, who is within 47 months of age, does not have any one of these four illnesses or another autoimmune disease. Subjects may enroll at the NIH Clinical Center in Bethesda or in their local doctors' offices. Patients remain under the care of their personal physicians while participating in the study. There is no charge for study-related evaluations and medical tests at the NIH.
For information about the NIH Twin-Sibs Study, call 1-800-411-1222.
The drug cyclophosphamide, in combination with the drug mesna, is being tested in patients with severe polymyositis who are unresponsive to steroid immunosuppressant therapy. This therapy may be beneficial, but more research is needed to determine the long-term safety and effectiveness.
Myositis Association of America, Inc. is conducting a survey of individuals with inflammatory myopathies, such as: dermatomyositis, polymyositis, and inclusion body myositis. For more information, conact the Myositis Association of America, Inc. listed in the resources section of this report.
A Phase II study of infliximab (Remicade) as a treatment for dermatomyositis and polymyositis is in progress at the NIH Warren G. Magnuson Clinical Center. It is sponsored by the Naitonal Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). For information, contact the NIH (see above).
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Polymyositis and Dermatomyositis: C.M. Pearson; Arthritis Medical Information Series, Arthritis Foundation, 1983.
Myositis-Specific Antibodies: Touchstones for Understanding the Inflammatory Myopathies. F. W. Miller; JAMA (Oct 20 1993; 270(15)). Pp. 1846-49.
Idiopathic Inflammatory Myopathies: Inclusion Body Myositis, Polymyositis and Dermatomyositis. V. W. Askanas et al.; Current Opinion in Neurology (1994; 7). Pp. 448-56.
Apolipoprotein E and Apolipotroein E Messenger RNA in Muscle of Inclusion Body Myositis and Myopathies. M. Mirabella et al.; Annals of Neurology (1996; 40). Pp. 864-872.
Report last updated: 2007/10/12 00:00:00 GMT+0