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Related to polymyositis: Polymyalgia rheumatica




Polymyositis is an inflammatory muscle disease causing weakness and pain. Dermatomyositis is identical to polymyositis with the addition of a characteristic skin rash.


Polymyositis (PM) is an inflammatory disorder in which muscle tissue becomes inflamed and deteriorates, causing weakness and pain. It is one of several types of inflammatory muscle disease, or myopathy. Others include dermatomyositis (DM) and inclusion body myositis. All three types are progressive conditions, usually beginning in adulthood. A fourth type, juvenile dermatomyositis, occurs in children. Although PM and DM can occur at any age, 60% of cases appear between the ages of 30 and 60. Females are affected twice as often as males.

Causes and symptoms


The cause of PM and DM is not known, but it is suspected that a variety of factors may play a role in the development of these diseases. PM and DM may be autoimmune diseases, caused by the immune system's attack on the body's own tissue. The reason for this attack is unknown, although some researchers believe that a combination of immune system susceptibility and an environmental trigger may explain at least some cases. Known environmental agents associated with PM and DM include infectious agents such as Toxoplasma, Borrella (Lyme disease bacterium), and coxsackievirus. Most cases, however, have no obvious triggers (direct causative agents). There may also be a genetic component in the development of PM and DM.


The early symptoms of PM and DM are slowly progressing muscle weakness, usually symmetrical between the two sides of the body. PM and DM affect primarily the muscles of the trunk and those closest to the trunk, while the hands, feet, and face usually are not involved. Weakness may cause difficulty walking, standing, and lifting objects. Rarely, the muscles of breathing may be affected. Weakness of themuscles used for swallowing can cause difficulty with swallowing (dysphagia). Joint pain and/or swelling also may be present. Later in the course of these diseases, muscle wasting or shortening (contracture) may develop in the arms or legs. Heart abnormalities, including electrocardiogram (ECG) changes and arrhythmias, develop at some time during the coursed of these diseases in about 30% of patients.
Dermatomyositis is marked by a skin rash. The rash is dusky, reddish, or lilac in color, and is most often seen on the eyelids, cheeks, bridge of the nose, and knuckles, as well as on the back, upper chest, knees, and elbows. The rash often appears before the muscle weakness.


PM and DM are often difficult diseases to diagnose, because they are rare, because symptoms come on slowly, and because they can be mistaken for other diseases that cause muscle weakness, especially limb girdle muscular dystrophy.
Accurate diagnosis involves:
  • A neurological exam.
  • Blood tests to determine the level of the muscle enzyme creatine kinase, whose presence in the circulation indicates muscle damage.
  • Electromyography, an electrical test of muscle function.
  • Muscle biopsy, in which a small sample of affected muscle is surgically removed for microscopic analysis. A biopsy revealing muscle cells surrounded by immune system cells is a strong indicator of myositis.


PM and DM respond to high doses of immunosuppressant drugs in most cases. The most common medication used is the corticosteroid prednisone. Prednisone therapy usually leads to improvement within two or three months, at which point the dose can be tapered to a lower level to avoid the significant side effects associated with high doses of prednisone. Unresponsive patients are often given a replacement or supplementary immunosuppressant, such as azathioprine, cyclosporine, or methotrexate. Intravenous immunoglobulin treatments may help some people who are unresponsive to other immunosuppressants.
Pain can usually be controlled with an over-the-counter analgesic, such as aspirin, ibuprofen, or naproxen. A speech-language therapist can help suggest exercises and tips to improve difficulty in swallowing. Avoiding weight gain helps prevent overtaxing weakened muscles.

Alternative treatment

As with all autoimmune conditions, food allergies/intolerances and environmental triggers may be contributing factors. For food allergies and intolerances, an elimination challenge diet can be used under the supervision of a trained practitioner, naturopath, or nutritionist, to identify trigger foods. These foods can then be eliminated from the person's diet. For environmental triggers, it is helpful to identify the source so that it can be avoided or eliminated. A thorough detoxification program can help alleviate symptoms and change the course of the disease. Dietary changes from processed foods to whole foods that do not include allergen triggers can have significant results. Nutrient supplements, especially the antioxidants zinc, selenium, and vitamins A, C, and E, can be beneficial. Constitutional homeopathic treatment can work at a deep level to rebalance the whole person. Acupuncture and Chinese herbs can be effective in symptom alleviation and deep healing. Visualization, guided imagery, and hypnosis for pain management are also useful.


The progression of PM and DM varies considerably from person to person. Immunosuppressants can improve strength, although not all patients respond, and relapses may occur. PM and DM can lead to increasing weakness and disability, although the life span usually is not significantly affected. About half of the patients recover and can discontinue treatment within five years of the onset of their symptoms. About 20% still have active disease requiring ongoing treatment after five years, and about 30% have inactive disease but some remaining muscle weakness.


There is no known way to prevent myositis, except to avoid exposure to those environmental agents that may be associated with some cases.



Dermatomyositis and Polymyositis Support Group. 146 Newtown Road, Southampton, SO2 9HR, U.K.
Muscular Dystrophy Association. 3300 East Sunrise Drive, Tucson, AZ 85718. (800) 572-1717. http://www.mdausa.org.
Myositis Association of America. 600-D University Boulevard, Harrisonburg, VA 22801. (540) 433-7686. http://www.myositis.org.
National Institutes of Health. National Institute of Arthritis and Musculoskeletal and Skin Diseases. 900 Rockville Pike, Bethesda, MD 20892. (301) 496-8188. 〈http://www.hih.gov.niams〉.

Key terms

Autoimmune disease — A diseases in which the body's immune system, responsible for fighting off foreign invaders such as bacteria and viruses, begins to attack and damage a part of the body as if it were foreign.
Immunosuppressant — A drug that reduces the body's natural immunity by suppressing the natural functioning of the immune system.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


a chronic, progressive inflammatory disease of skeletal muscle, occurring in both children and adults, and characterized by symmetrical weakness of the limb girdles, neck, and pharynx, usually associated with pain and tenderness, and sometimes preceded or followed by manifestations typical of scleroderma, arthritis, systemic lupus erythematosus, or Sjögren's syndrome. It is also sometimes associated with malignancy, and may be accompanied by characteristic skin lesions.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Inflammation of a number of voluntary muscles simultaneously.
[poly- + G. mys, muscle, + -itis, inflammation]
Farlex Partner Medical Dictionary © Farlex 2012


A disease characterized by chronic inflammation of the skeletal muscles and progressive muscle weakness.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Rheumatology An inflammatory myopathy of adults that may be acute, subacute, or chronic; predominant feature is symmetrical proximal muscle weakness of insidious onset; polymyositis is accompanied by EMG changes, muscle necrosis, ↑ creatinine phosphokinase, skin lesions, myalgias, tenderness, later atrophy and fibrosis; the criteria for defining polymyositis–and dermatomyositis are those of Bohan and Peter  Treatment Corticosteroids; if refractory, MTX, RT. See Polymyositis-dermatomyositis.


Rheumatology An 'overlap' syndrome where polymyositis and dermatomyositis share multiple features–proximal distribution of muscle weakness, typical skin changes, 'machinist's hands', chronic 'round cell' inflammation, IgM rheumatoid factor, myopathic changes, spontaneous electrical discharges by EMG, response to corticosteroids. See Machinist's hands, Polymyositis.
Polymyositis-dermatomyositis–defining criteria
1.  Symmetric proximal/limb-girdle muscle weakness of insidious onset
2.  Typical skeletal pathology–eg, presence of 'skip' areas of involvement
3.  ↑ Serum levels of skeletal muscle enzymes–ALA, aldolase, AST, CK-MM, LDH
4.  A characteristic EMG triad of brief small polyphasic motor unit potentials, fibrillation potentials, positive waves, insertion irritability, and normal conduction velocity
Dermatomyositis is defined by a final criterion
5.  Lilac/heliotrope discoloration of eyelids, periorbital edema; characteristic scaling erythematous rash over dorsal aspect of hands–Gottron sign, involvement of elbows, knees, medial malleoli and upper body  
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Inflammation of several voluntary muscles simultaneously.
[poly- + G. mys, muscle, + -itis, inflammation]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A rare, inflammatory, AUTOIMMUNE disease of muscles causing pain, tenderness and muscle weakness. Polymyositis is often associated with skin changes (DERMATOMYOSITIS) and responds to treatment with corticosteroid drugs.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Patient discussion about polymyositis

Q. Does my son have dermatomyositis? My son is 6 years old and he is very weak. He gets very tired after doing the simplest things like going for a walk. He also has a rash on his neck. What could this be?

A. It doesn't sound like you have anything to worry about. The main warning sign of dermatomyositis is muscle weakness. Usually the first muscles affected are in the hips and thighs, though any other muscle in the body can be affected. It may be hard to climb stairs, get dressed or get out of bed.
Pain in the joints between bones.
Deep red (almost purple) rash, usually on the face, scalp, neck and chest. However, the rash can appear on any part of the body.
Coughing and shortness of breath.
· It may also be hard to swallow.
If you have dermatomyositis you will have muscle weakness and will develop a rash, most often on your face, scalp, neck and chest. The rash can also appear on your hands and fingers (often the knuckles), elbows, knees, ankles, upper arms and thighs. The rash is often deep red in colour (almost purple) and in some areas may be slightly raised. If your son's rash doesn't look like this then it could be caused by many other things, consult your Dr about it.

More discussions about polymyositis
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References in periodicals archive ?
Studies have placed the highest risk of concomitant malignancy with dermatomyositis and the least risk with polymyositis. (The relative risk for malignancy in dermatomyositis as compared with polymyositis was 2.4.) Malignancy associated with dermatomyositis or polymyositis is twice as likely in women than in men.
Aoki, "Clinical values of FDG PET in polymyositis and dermatomyositis syndromes: imaging of skeletal muscle inflammation," BMJ Open, vol.
Increased expression of the NOD-like receptor family, pyrin domain containing 3 inflammasome in dermatomyositis and polymyositis is a potential contributor to their pathogenesis.
Myoglobinuria and acute renal failure with acute polymyositis. N Y State J Med 1979;79:764-7.
Classification criteria for polymyositis and dermatomyositis.
Anti-synthetase syndrome: a new autoantibody to phenylalanyl transfer RNA synthetase (anti-Zo) associated with polymyositis and interstitial pneumonia.
Interstitial lung disease in polymyositis and dermatomyositis: clinical features and prognosis as correlated with histologic findings.
Engel, "Cardiac manifestations in polymyositis," The American Journal of Cardiology, vol.
Lundberg, "Interstitial lung disease in polymyositis and dermatomyositis," Current Opinion in Rheumatology, vol.
Vascular manifestations of dermatomyositis and polymyositis. Clinical, capillaroscopic and histological aspects.
However, specific forms of myositis like dermatomyositis and polymyositis occur when the body's immune system turns against its own muscles, damaging the muscle tissue in the process.