What are polymyositis and dermatomyositis?
Polymyositis and dermatomyositis are disease of muscle featuring inflammation of the muscle fibers. The cause of the disease is not known. It begins when white blood cells, the immune cells of inflammation, spontaneously invade muscles. The muscles affected are typically those closest to the trunk or torso. This results in a weakness that can be severe. Polymyositis is a chronic illness featuring progressive muscle weakness with periods of increased symptoms, called flares or relapses, and minimal or no symptoms, known as remissions.
Polymyositis is slightly more common in females. It affects all age groups, although its onset is most common in middle childhood and in the 20s. Polymyositis occurs throughout the world. Polymyositis can be associated with a characteristic skin rash and is then referred to as "dermatomyositis." Dermatomyositis in children is referred to as juvenile dermatomyositis. "Amyopathic dermatomyositis" is the term used to describe people who have skin changes compatible with dermatomyositis but do not have diseased muscle involvement.
Polymyositis can also affect other areas of the body and is, therefore, referred to as a systemic illness. Occasionally, it is associated with cancer or with other diseases of connective tissue (such as systemic lupus erythematosus, scleroderma, and rheumatoid arthritis). Depending on which other diseases it is associated with, it may be referred to as an "overlap syndrome" or "mixed connective tissue disease."
What causes polymyositis and dermatomyositis?
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 have found 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).
What are the symptoms of polymyositis and dermatomyositis?
The weakness of muscles is the most common symptom of polymyositis. The muscles involved usually are those that are closest to the trunk of the body. Both sides of the body are affected. The onset can be gradual or rapid. This results in varying degrees of loss of muscle power and atrophy. The loss of strength can be noticed as difficulty getting up from chairs, walking, climbing stairs, or lifting above the shoulders. The trouble with swallowing and weakness lifting the head from the pillow can occur. Occasionally, the muscles ache and are tender to the touch.
- Patients can also feel fatigued, a general feeling of discomfort, and have weight loss and/or low-grade fever.
- The weakness of the muscles that produce the voice can lead to a weak-sounding voice (dysphonia).
With skin involvement (dermatomyositis), the eyes can be surrounded by a violet discoloration with swelling.
- There can be scaly reddish discoloration over the knuckles, elbows, and knees (Gottron's sign).
- There can also be a reddish rash on the face, neck, and upper chest.
- The skin changes can occur with or before the development of muscle weakness.
- Hard lumps of calcium deposits can develop in the fatty layer of the skin, most commonly in childhood dermatomyositis.
Heart and lung involvement can lead to
Because polymyositis can appear in combination with other illnesses (see related articles on systemic lupus erythematosus, scleroderma, and rheumatoid arthritis), it can also have overlap features with them. These illnesses are discussed elsewhere.
Both polymyositis and dermatomyositis can sometimes be associated with cancers, including
The cancer risk is reported to be much greater with dermatomyositis than polymyositis.
Diagnosis of polymyositis or dermatomyositis
When a patient first sees the doctor, the recent symptoms especially concerning weakness will be discussed. The condition of many other body areas might be reviewed, for example, the skin, heart, lungs, and joints. An examination will further focus on these and other systems. Various measures of strength might be noted. The characteristic features of polymyositis include weakness of the muscles closest to the trunk of the body, abnormal elevation of muscle enzymes, electromyography (EMG) findings, magnetic resonance imaging (MRI) findings, and certain abnormalities detected with muscle biopsy.
- Blood testing usually (but not always) reveals abnormally high levels of muscle enzymes, CPK or creatinine phosphokinase, aldolase, SGOT, SGPT, and LDH. These enzymes are released into the blood by a muscle that is being damaged by inflammation. They can also be used as measures of the activity of the inflammation. Other routine blood and urine tests can also look for internal organ abnormalities.
- Chest X-rays, mammograms,
- Pap smears, and
- other screening tests might be considered.
- Autoantibodies can often be found in the blood of people with polymyositis.
- These include antinuclear antibodies (ANAs) and myositis-specific antibodies (such as Jo-1 antibody).
- Electromyography (EMG) and nerve conduction velocity are electrical tests of muscle and nerves that can show abnormal findings typical of polymyositis as well as exclude other nerve-muscle diseases.
- Imaging of the muscles using radiology tests, such as magnetic resonance imaging (MRI scanning), can show areas of inflammation of muscle. This sometimes can be used to determine optimal muscle biopsy sites.
- A muscle biopsy is used to confirm the presence of muscle inflammation typical only of polymyositis. This is a surgical procedure whereby muscle tissue is removed for analysis by a pathologist, a specialist in examining the tissue under a microscope. Muscles often used for biopsy include the quadriceps muscle of the front of the thigh, the biceps muscle of the arm, and the deltoid muscle of the shoulder.
Polymyositis is typically treated by rheumatologists. Others who can be involved in the care of patients with polymyositis include internists, pathologists, dermatologists, radiologists, cardiologists, neurologists, surgeons, and physiatrists.
What is the treatment for polymyositis and dermatomyositis?
Initially, polymyositis is treated with high doses of corticosteroids. Corticosteroids are cortisone medications (such as prednisone and prednisolone). These are medications related to cortisone and can be given by mouth or intravenously. They are given because they can have a powerful effect to decrease the inflammation in the muscles. They usually are required for years, and their continued use will be based on what the doctor finds related to symptoms, examination, and muscle enzyme blood test.
Corticosteroids have many predictable and unpredictable side effects.
- In high doses, they commonly cause an increase in appetite and weight,
- puffiness of the face, and
- easy bruising.
- They can also cause sweats,
- facial-hair growth,
- upset stomach,
- sensitive emotions,
- leg swelling,
- high blood pressure,
- worsening of diabetes, and
- increased risk of infection.
- A rare complication of cortisone medications is severe bone damage (avascular necrosis) which can destroy large joints, such as the hips and shoulders.
Corticosteroids do not always adequately improve polymyositis. In these patients, immunosuppressive medications are considered.
- These medications can be effective by suppressing the immune response that attracts the white blood cells of inflammation to the muscles.
- Many types are now commonly used and others are still experimental.
- Methotrexate (Rheumatrex, Trexall) can be taken by mouth or by injection into the body.
- Azathioprine (Imuran) is an oral drug.
- Both can cause liver and bone-marrow side effects and require regular blood monitoring.
- Cyclophosphamide (Cytoxan), chlorambucil (Leukeran), and cyclosporine (Sandimmune) have been used for serious complications of severe diseases, such as scarring of the lungs (pulmonary fibrosis). These also can have severe side effects which must be considered with each patient individually.
- Treatment with intravenous infusion of immunoglobulins (IVIG) is effective in severe cases of polymyositis that are resistant to other treatments. Recent research reports indicate that intravenous rituximab (Rituxan) may help treat resistant disease.
- Patients with calcium deposits (calcinosis) from dermatomyositis can sometimes benefit from taking diltiazem (Cardizem) to shrink the size of the calcium deposits. This effect, however, occurs slowly (frequently over years) and is not always effective. The complication of calcium deposits in muscles and soft tissues occurs more frequently in children than adults.
- Physical therapy with gradual muscle strengthening is an important part of the treatment of polymyositis. When to begin and the continued degree of exercise and range of motion of extremities is customized for each patient.
Patients can ultimately do well, especially with early medical treatment of disease and disease flares. The disease frequently becomes inactive, and rehabilitation of atrophied muscle becomes a long-term project. Monitoring for signs of cancer, heart, and lung disease is essential. Accordingly, EKG, lung function testing, and X-ray tests are used.
As mentioned above, the related muscle disease called inclusion body myositis is often more resistant to treatment than polymyositis. As scientists better define the specific causes of the different forms of polymyositis, treatment will be more accurately aimed at the cure of this disease. Researchers are finding more specific antibodies in patients that may be used to diagnose and define the active disease.
The best home remedy is to closely monitor the condition with the physician and physical therapist. It is best to not over-exercise early on but gradually increase exercise for optimal results.
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What are complications of polymyositis and dermatomyositis?
Cancer screening is performed, especially in patients with dermatomyositis, due to an increased risk of cancer in patients with muscle inflammation.
What is the prognosis for polymyositis and dermatomyositis?
The outcome for patients with polymyositis varies. While some have a relatively brief illness followed by remission not requiring subsequent treatment, others develop episodes of remissions and exacerbations requiring more or less treatment.
The presence of Jo-1 antibody, a myositis antibody, is predictive of an increased risk for the development of inflammation of the tissues of the lungs (interstitial lung disease). This can lead to permanent suboptimal lung function. Pulmonary function testing can be used to detect early lung abnormalities.
Is it possible to prevent polymyositis and dermatomyositis?
There is no prevention for polymyositis. When the precise cause of polymyositis is identified, preventative measures might be possible.
Koopman, William, et al., eds. Clinical Primer of Rheumatology. Philadelphia: Lippincott Williams & Wilkins, 2003.
Ruddy, Shaun, et al., eds. Kelley's Textbook of Rheumatology. Philadelphia: W.B. Saunders Co., 2000.
Top Polymyositis Related Articles
Antinuclear Antibody TestAntinuclear antibodies (ANAs), unusual antibodies that can bind to certain structures within the nucleus of the cells, are found in patients whose immune system may be predisposed to cause inflammation against their own body tissues. ANAs are indicative of the potential presence of an autoimmune illness.
Body Pain: What Does It Mean When Your Whole Body Aches?Body aches are a symptom of the flu, arthritis, autoimmune disease, infections like Lyme disease, and other conditions. Body pain and muscle aches may accompany fever, headache, and other symptoms. Body aches are a general symptom of many potential underlying conditions. Only a doctor can diagnose and treat the cause.
CT Scan vs. MRI
CT scan (computerized tomography) is a procedure that uses X-rays to scan and take images of cross-sections of parts of the body. CT scan can help diagnose broken bones, tumors or lesions in areas of the body, blood clots in the brain, legs, and lung, and lung infections or diseases like pneumonia or emphysema.
MRI (magnetic resonance imaging) is a procedure that uses strong magnetic fields and radiofrequency energy to make images of parts of the body, particularly, the organs and soft tissues like tendons and cartilage.
Both CT and MRI are painless, however, MRI can be more bothersome to some individuals who are claustrophobic, or suffer from anxiety or panic disorders due to the enclosed space and noise, the machine makes.
MRI costs more than CT, while CT is a quicker and more comfortable test for the patient.
Dermatomyositis PictureDermatomyositis. Dermatomyositis is a rare autoimmune disease that is characterized by a distinctive red or purplish rash as well as muscle weakness. It usually shows up where muscles are used to straighten joints like knuckles, elbows, knees, toes or even eyelids. Hard painful lumps can occur, most often in children.
Electromyogram (EMG)Electromyogram or EMG is defined as a test that records the electrical activity of muscles. Normal muscles produce a typical pattern of electrical current that is usually proportional to the level of muscle activity. Diseases of muscle and/or nerves can produce abnormal electromyogram patterns.
Apheresis (Hemapheresis, Pheresis)Apheresis (hemapheresis, pheresis) is a process of removing a specific component from the blood of a donor or patient that contains disease-provoking elements. Forms of apheresis include:
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Mixed Connective Tissue Disease (MCTD)Mixed connective tissue disease (MCTD), as first described in 1972, is classically considered an overlap of three diseases: systemic lupus erythematosus, scleroderma, and polymyositis. Patients with this pattern of illness have features of each of these three diseases.
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SclerodermaScleroderma is an autoimmune disease of the connective tissue. It is characterized by the formation of scar tissue (fibrosis) in the skin and organs of the body, leading to thickness and firmness of involved areas. Scleroderma is also referred to as systemic sclerosis, and the cause is unknown. Treatment of scleroderma is directed toward the individual features that are most troubling to the patient.
Swallowing Problems (Dysphagia)Dysphagia or difficulty in swallowing, swallowing problems. Dysphagia is due to problems in nerve or muscle control. It is common, for example, after a stroke. Dysphagia compromises nutrition and hydration and may lead to aspiration pneumonia and dehydration.
Lupus (Systemic Lupus Erythematosus or SLE)Systemic lupus erythematosus is a condition characterized by chronic inflammation of body tissues caused by autoimmune disease. Lupus can cause disease of the skin, heart, lungs, kidneys, joints, and nervous system. When only the skin is involved, the condition is called discoid lupus. When internal organs are involved, the condition is called systemic lupus erythematosus (SLE).