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Diseases and Conditions
Polymyositis
From MayoClinic.com
Special to CNN.com

Introduction

Polymyositis (pol-e-mi-o-SI-tis) is an uncommon disease that causes inflammation in your muscles. Doctors also refer to polymyositis as a type of connective tissue disease. Its most noticeable characteristic is muscle weakness, especially in the muscles closest to your trunk, such as your shoulder and hip muscles. As a result, you may find it difficult to get out of chairs, climb stairs, brush your hair or work with your arms over your head. Polymyositis is rarely fatal, but it can be disabling in its more severe forms.

Although polymyositis can occur at any age, it mostly affects adults in their 40s and 50s. It is more common in blacks than in whites, and women have it more often than men do. Polymyositis usually develops gradually over weeks or months.

Periods of remission, during which signs and symptoms improve spontaneously, rarely occur in polymyositis. However, treatment can improve your muscle strength and function.

Signs and symptoms

Signs and symptoms of polymyositis usually appear gradually, so it may be difficult to pinpoint when they first started. They may also fluctuate from week to week or month to month. The most common signs and symptoms include:

  • Progressive muscle weakness, particularly in the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. This weakness is symmetrical, affecting both the left and right sides of your body.
  • Difficulty swallowing (dysphagia).
  • Mild joint or muscle tenderness.
  • Fatigue.

Causes

Polymyositis belongs to a group of conditions called inflammatory myopathies. Myopathies are diseases or abnormal conditions of the striated muscles that cover your skeleton. The cause of most inflammatory myopathies is unknown. Infections caused by bacteria, parasites or viruses can cause inflammatory myopathies, but in most cases, doctors aren't able to identify a preceding infection in polymyositis.

A disease similar to polymyositis is dermatomyositis. Dermatomyositis leads to many of the same symptoms as polymyositis, but it causes skin inflammation or a rash as well. Other inflammatory muscle diseases include inclusion body myositis, which progresses more slowly than other forms; myositis associated with other connective tissue diseases, such as lupus or scleroderma; and myositis associated with cancer (malignancy).

Doctors suspect that myopathies are autoimmune disorders, in which your body's immune system mistakes normal components of your body for foreign substances and attacks them. If you have polymyositis, an unknown cause seems to trigger your immune system to begin producing autoimmune antibodies (also called autoantibodies) that may damage healthy body tissues. Many people with polymyositis show a detectable level of autoantibodies in their blood. It's still unclear, however, whether these autoantibodies are indeed involved in causing polymyositis.

Polymyositis has also been associated with several viral diseases, including HIV. Some researchers speculate that, in some form, polymyositis may be caused by a viral infection of the muscle. This theory isn't well supported, however.

When to seek medical advice

If you experience weakness in your shoulder and hip muscles for a continued period, see your doctor. The earlier polymyositis is detected, the better your response may be to treatment. With treatment, you can manage and sometimes even reverse your signs and symptoms. If your doctor thinks you may have polymyositis, he or she may refer you to a specialist, such as a rheumatologist or a neurologist.

If you have difficulty swallowing or shortness of breath, call your doctor right away, as this may indicate the need for immediate help.

Screening and diagnosis

Diagnosis of polymyositis isn't always easy and can be a lengthy process. Even though the attempt to diagnose your condition may be frustrating, remember that an accurate diagnosis is necessary to receive appropriate treatment.

In addition to a thorough physical exam, including assessment of your muscle strength, your doctor will likely use some or all of the following information and tests to assist in the diagnosis:

  • Family medical history. A careful history of muscle disease in your family and your own age at onset of the disease will help your doctor distinguish between polymyositis and muscular dystrophy. Muscular dystrophy is an inherited condition; its signs and symptoms usually begin in early childhood.
  • Electromyography. A thin needle electrode is inserted through your skin into the muscle to be tested. Electrical activity is measured as you relax or tighten the muscle. Changes in the pattern of electrical activity can confirm a muscle disease. The distribution of the disease can be determined by testing different muscles.
  • Blood analysis. A blood test can let your doctor know if you have elevated levels of muscle enzymes, such as creatine kinase (CK) and aldolase. Increased CK and aldolase levels can indicate muscle damage. A blood test can also determine whether autoantibodies are present in your blood.
  • Muscle biopsy. A small piece of muscle tissue is removed surgically for laboratory analysis. A muscle biopsy may reveal abnormalities in your muscles, such as inflammation, damage or infection. The sample also can be examined for the presence of abnormal proteins and checked for enzyme deficiencies.
  • Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. These images can be viewed from any direction or plane. During the test you lie inside the cylindrical-shaped scanner for 15 minutes to an hour. MRI scans may help detect inflammation in your muscles.

Complications

If the muscles in your esophagus are affected, you may have problems swallowing (dysphagia), which in turn may cause weight loss and malnutrition. Dysphagia may also lead to entrance of food or liquids, including saliva, into your lungs (aspiration), which can result in pneumonia. If your chest muscles are involved, you may experience breathing problems, such as shortness of breath. Deposits of calcium in your muscles, skin and connective tissues (calcinosis) can occur late in the disease, particularly if you've had the disease for a long time.

Polymyositis is often associated with other conditions, including:

  • Other connective tissue diseases. Diseases such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome can occur in combination with polymyositis.
  • Cardiovascular disease. The muscle of your heart may become inflamed (myocarditis). In a small number of people who have polymyositis, congestive heart failure and heart arrhythmias may develop.
  • Lung disease. A condition called interstitial lung disease may occur with polymyositis. Interstitial lung disease refers to a group of disorders that cause inflammation and scarring (fibrosis) of lung tissue, making lungs stiff and inelastic. Signs and symptoms include a dry cough and shortness of breath. In the late stage of lung disease, high blood pressure in the pulmonary arteries (pulmonary hypertension) can occur and can lead to right-sided heart failure.
  • Cancer. Cancer may be more common in people with polymyositis, but the evidence for this association is more pronounced in dermatomyositis.

Pregnancy may worsen signs and symptoms in women whose disease is active. Active polymyositis can also increase the risk of premature birth or stillbirth. If the disease is in remission, the risk isn't as great.

People with polymyositis or dermatomyositis may also be at an increased risk of infections, particularly respiratory and digestive infections. As a result, your doctor may monitor your signs and symptoms for any indication of infection so that you can receive prompt diagnosis and treatment.

Treatment

Although there's no cure for polymyositis, treatment can improve your muscle strength and function. Treatment begun early in the disease process tends to be more effective, often because there are fewer complications. Methods of therapy include the following:

  • Corticosteroids. These medications suppress your immune system, limiting the production of antibodies and reducing muscle inflammation. Corticosteroids, especially prednisone, are usually the first choice in treating inflammatory myopathies, such as polymyositis. Your doctor may begin with a very high dose then decrease it as your symptoms improve. This generally takes about two to four weeks. Significant results are usually evident within three to six months, but therapy is often needed for years. Prolonged use of corticosteroids can have serious side effects including osteoporosis, weight gain, diabetes, increased risk of some infections, mood swings, cataracts, high blood pressure, a redistribution of body fat and muscle weakness. As a result, your doctor may also recommend supplements such as calcium and vitamin D and may prescribe bisphosphonates such as alendronate (Fosamax) or risedronate (Actonel).
  • Other immunosuppressants. If your body doesn't respond adequately to corticosteroids, your doctor may recommend other immunosuppressive drugs such as azathioprine (Imuran) or methotrexate (Rheumatrex). Your doctor may prescribe these alone or in combination with corticosteroids. When in combination, these additional immunosuppressants can be used to lessen the dose and potential side effects of the corticosteroid. Immunosuppressants such as cyclophosphamide (Cytoxan) and cyclosporine (Neoral, Sandimmune) may improve symptoms of polymyositis and interstitial lung disease.
  • Physical therapy. A physical therapist can show you various exercises to maintain and improve your strength and flexibility and advise an appropriate level of activity. Your exercise program is likely to change during the course of the disease and treatment period. Staying active will help maintain muscle strength.

Treatments with unknown long-term effects include:

  • Intravenous immunoglobulin (IVIg). This involves receiving intravenous infusions of antibodies from a group of donors over two to five days.
  • Plasmapheresis. This treatment, also called plasma exchange, is a type of blood cleansing in which damaging antibodies are removed from your blood.
  • Radiation therapy. This involves irradiation of the lymph nodes to suppress your immune system.

Treatments that are still in the experimental phase but have shown signs of being effective include fludarabine (Fludara), an agent that prevents the development and growth of malignant cells, and tacrolimus (Prograf), a transplant rejection drug that may work to inhibit your immune system.

Coping skills

Living with a chronic autoimmune disease can make you wonder at times whether you're up to the challenge. Though it isn't always easy, you're tougher than you think. To help you cope, try supplementing your medical care with the following suggestions:

  • Know your illness. Read all you can about polymyositis and other muscle and autoimmune disorders. Attend lectures and talk to people who have a similar condition. Don't be afraid to ask your doctor any questions concerning your illness, diagnosis or treatment plan.
  • Be a part of your medical team. Consider yourself a member of your medical team in the fight against your disease. Following the treatment plan you agreed to is vital. Keep your doctor updated on any new signs or symptoms you may experience. Regularly perform the physical exercises prescribed for you.
  • Rest before you get tired. Don't wait until you're exhausted to rest. This will only set you back further as your body tries to recuperate. Learning to pace yourself can help you maintain a consistent level of energy, accomplish just as much and feel better emotionally. Learn to say no effectively and ask for help when you need it.
  • Use electric appliances and power tools. Save your energy by using power appliances, such as battery-operated toothbrushes, electric can openers and power screwdrivers.
  • Accept your emotions. Denial, anger and frustration are normal feelings when you must deal with an illness. Things don't seem normal or fair and likely seem out of your control. Feelings of fear and isolation are common, so stay close to your family and friends. Try to maintain your daily routine as best you can and don't neglect doing those things you enjoy. Many people find support groups to be a helpful resource.

  • Video: Therapeutic plasmapheresis
  • Polymyositis: Can a gluten-free diet improve signs and symptoms?
  • July 14, 2005

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