What is polymyositis?

  1. What is polymyositis? Polymyositis is an inflammatory muscle disease that causes muscle weakness. Myositis means inflammation of muscle. Usually, polymyositis affects the muscles that are closest to the trunk of the body. Eventually, people with polymyositis have trouble when rising from a sitting position, climbing stairs, lifting objects, or reaching overhead. In some cases, muscles that are not close to the trunk of the body become affected as the disease progresses. Polymyositis develops gradually over time, and it rarely affects people younger than 18. It is more common in women (by about two to one). If the condition is accompanied by an inflammatory process that strikes the skin as well, it is called dermatomyositis. Polymyositis can be present in combination with other illnesses. Both polymyositis and dermatomyositis can sometimes be associated with cancers, including lymphoma, breast, lung, ovarian, and colon cancer. What causes polymyositis? The cause of polymyositis is not known, but there are indications that heredity plays a role in the disease. Current research suggests that the condition might occur when immune system cells infiltrate and attack muscle tissue (an autoimmune process). Research into the workings of the immune system and what causes it to malfunction might result in more knowledge about the causes of polymyositis. What are the symptoms of polymyositis? The following are some symptoms of polymyositis. These symptoms might come and go: * Muscle weakness—This is the most common symptom. The muscles involved usually are those closest to the trunk of the body. The onset of weakness is usually gradual, occurring over three to six months or, rarely, the symptoms come on rapidly. * Difficulty getting up from chairs, climbing stairs, or lifting objects — Some people also have trouble with getting up after lying down. * Difficulty swallowing * Muscle ache — In some cases, muscles ache and are tender to the touch. * Fatigue * Shortness of breath due to heart and lung involvement * Patchy red or violet rash around the eyes — Some people also get patchy, red skin over the knuckles, elbows, and knees, or a red rash on the neck and upper chest. * Fever * Weight loss How is polymyositis diagnosed? The diagnosis of the disease usually begins with a doctor’s exam, as well as blood testing. People who have polymyositis often have unusually high levels of muscle enzymes, which are released into the blood by muscle that is being damaged by inflammation. Routine blood and urine tests can check for internal organ abnormalities. Chest X-rays, mammograms, PAP smears, and other screening tests might be considered to look for signs of cancers that might arise with polymyositis. Additional testing can rule out other conditions resembling polymyositis. Electromyography (EMG) and nerve conduction velocity studies are electrical tests of muscle and nerves that can show abnormal findings typical of polymyositis. These tests also can rule out other nerve-muscle diseases. Imaging of the muscles can show areas of muscle inflammation and can be used to find muscle biopsy sites. Muscle biopsy is a surgical procedure in which muscle tissue is removed and examined. A muscle biopsy is used to confirm the presence of muscle inflammation typical only of polymyositis. How is polymyositis treated? Polymyositis is treated with high doses of corticosteroids as a first course of treatment. Corticosteroids are given because they can effectively decrease the inflammation in the muscles. Corticosteroids do not always adequately improve polymyositis. In these patients immunosuppressive medicines are considered. These medicines include: * Methotrexate (brand names Rheumatrex and Trexall) * Azathioprine (brand name Imuran) * Cyclophosphamide (brand name Cytoxan) * Chlorambucil (brand name Leukeran) * Cyclosporine (brand name Sandimmune) In severe cases of polymyositis, the intravenous infusion of immunoglobulin (IVIG) has been an effective treatment. Physical therapy also is important in the treatment of polymyositis. With early medical treatment of the disease and disease flares, patients with polymyositis can do well. The disease frequently becomes inactive, enabling the patient to focus on muscle rehabilitation. What is dermatomyositis? When the inflammatory muscle disease polymyositis affects the skin, it is called dermatomyositis. In this condition, the eyes can be surrounded by a violet discoloration with swelling. There might be scaly, red skin over the knuckles, elbows, and knees. In addition, a red rash can occur on the face, neck, and upper chest. Hard lumps of calcium deposits can develop in the fatty layer of the skin. What causes dermatomyositis? In people with polymyositis and dermatomyositis, the body’s immune system stops working properly and begins attacking healthy tissues. Factors triggering this process are not known. What are the symptoms of dermatomyositis? Symptoms of dermatomyositis can vary a great deal from patient to patient. Some individuals might have the disease for months or years before noticing it. Muscle weakness might arise at the same time as the rash, or it might occur weeks, months, or years later. Some other common symptoms include: * Reddish or bluish-purple patches, mostly on areas exposed to the sun * Purple spots on bony prominences, especially the knuckles * Discoloration with swelling around the eyes * Ragged cuticles and prominent blood vessels on nail folds * A red rash on the face, neck, shoulders, upper chest, and elbows How is dermatomyositis diagnosed? The diagnosis of dermatomyositis is usually confirmed by the following tests: * Blood tests to detect increased amounts of muscle enzymes such as creatine kinase (CK) and sometimes lactic dehydrogenase (LDH) * Blood tests to detect auto-antibodies (antibodies that react with cells, tissues, or native proteins of the individual in which the antibodies are produced) * Skin biopsy of the rash * Biopsy of an affected muscle * Electromyography (EMG) testing * Magnetic resonance imaging (MRI) scan of muscles How is dermatomyositis treated? Doctors usually begin treatment of dermatomyositis with steroid drugs such as Prednisone. Immunosuppressants (Imuran, methotrexate) might be helpful for patients who are not helped by Prednisone. Further treatment with intravenous immunoglobulin (IVIG), used to slow down the autoimmune process, has been shown to be effective and safe. Physical therapy can preserve muscle function and prevent muscle wasting. What is inclusion body myositis (IBM)? Inclusion body myositis (IBM) is an inflammatory and degenerative muscle disease that causes painless weakening of muscles. IBM progresses slowly and is sometimes misdiagnosed as treatment-resistant polymyositis, another inflammatory muscle disease that causes muscle weakness. IBM also might be misdiagnosed as amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease). Symptoms of the disease usually begin after the age of 50, although the disease can occur earlier. IBM occurs more frequently in men than in women, and is the most common muscle disease in people aged 50 and older. What causes IBM? The cause of IBM is unknown. Because of the inflammation associated with IBM, some doctors think the disease is a form of autoimmune disorder. In this kind of disorder, the body’s immune system goes awry and attacks its own tissues — in this case, the muscles. Some experts have linked IBM to infection by a virus that has yet to be identified. Other researchers believe that the primary problem in IBM is an age-related inability of the muscle to deal with destructive chemicals. What are the symptoms of IBM? In IBM, the onset of muscle weakness usually is gradual, occurring over months or years. Falling and tripping usually are the first noticeable symptoms. For some people, IBM begins with weakness in the hands. People with IBM might have: * Difficulty with gripping, pinching, and buttoning * Weakness of the wrist and finger muscles * Atrophy (shrinking or wasting) of the muscles of the forearms * Weakness and visible wasting of the quadriceps muscles (the large muscles on the front part of the thighs) * Weakness of the lower leg muscles, below the knees * Weakness of the esophageal muscles, which can cause dysphagia (difficulty swallowing)—This occurs in about 20 percent t 40 percent of patients * Weakness of other muscle groups as the disease progresses How is IBM diagnosed? Doctors use a muscle biopsy to diagnose IBM. After administering an anesthetic, a doctor takes a sample of tissue from one of the affected muscles to be looked at in a laboratory. When viewed under the microscope, the muscle cells of a person with IBM contain vacuoles (rounded empty spaces). Within the vacuoles, there are usually abnormal clumps of several proteins including one called amyloid. The protein clumps, or inclusion bodies, give IBM its name. This is the hallmark of IBM. How is IBM treated? There is no effective course of treatment for IBM. The disease is unresponsive to corticosteroids and immunosuppressive drugs — two drugs that often treat inflammatory or autoimmune conditions. Some evidence suggests that intravenous immunoglobulin might help slightly in a small number of cases, but the benefit does not last long. Physical therapy might be helpful in maintaining mobility and helping to keep joints mobile. Other therapy, including treatments for the swallowing problems, is symptomatic and supportive.

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