Facts About Inflammatory Myopathies
Dermatomyositis (DM), Polymyositis (PM)
& Inclusion-Body Myositis (IBM)

Introduction Letter from Maureen McGovern Questions and Answers The Immune System Diagnosis and Treatment MDA's Search for a Cause, Treatment and Cure

DIAGNOSIS AND TREATMENT How is myositis diagnosed? If your doctor thinks you may have polymyositis or dermatomyositis, you should contact your local MDA office to arrange an examination at an MDA clinic. Diagnosis of PM and DM begins with a careful medical history and a physical exam. A neurological exam is used to test reflexes, strength and the distribution of weakness. Several specialized tests are used to confirm a suspected diagnosis of PM or DM. Electromyography (EMG) uses small needle electrodes to measure the electrical currents in a muscle as it contracts. While an EMG can't definitively diagnose PM or DM, it can be used to rule out a number of other types of neuromuscular disease that cause similar patterns of weakness. A creatine kinase (CK) test is a blood test for a muscle protein whose concentration in the blood rises with muscle damage. A blood sample is also used for antibody testing, to determine whether self-reactive (autoimmune) antibodies are present. A muscle biopsy requires the removal of a small piece of muscle tissue for microscopic analysis. The procedure is done either surgically, with an incision to expose the target muscle, or with a needle. A needle biopsy is faster and doesn't leave a scar, but removes less tissue, making its diagnostic value somewhat lower. Magnetic resonance imaging (MRI) may be used to identify areas of inflammation or replacement of muscle with fatty or fibrous tissue. None of these tests can by itself definitively establish a diagnosis of PM or DM, although consistent results among all of them are highly informative. Diagnosis of dermatomyositis for those with a typical rash is usually not difficult. Establishing a firm diagnosis of polymyositis in cases without consistent findings can be a frustrating experience for both the doctor and the patient. Misdiagnosis is relatively common for polymyositis, and is one important reason for taking advantage of the diagnostic services of an MDA clinic. How is myositis treated? The first-line treatment of both PM and DM is almost always oral prednisone, a corticosteroid hormone that suppresses the immune system. A high initial dose is continued long enough to improve strength and to reduce the CK levels in the blood, usually one to two months. The dose is then tapered over several months to a lower level, which may be maintained for a year or more to prevent recurrence. Prednisone can cause significant side effects, including weight gain, puffy features, osteoporosis (brittle bones), diabetes and mood changes. Up to one half of those with PM or DM don't have an adequate response to prednisone, and require other immunosuppressive drugs. The most common agents are azathioprine and methotrexate. Cyclophosphamide, chlorambucil and cyclosporine are also sometimes prescribed. The prednisone dose can often be reduced when another immunosuppressant is used. In some cases, intravenous methylprednisone or methotrexate may be used to treat the disease more aggressively. Intravenous immunoglobulin (IVIg) is used for those who have severe weakness or are unresponsive to other therapy. IVIg is a mixture of human blood proteins injected in large quantity into the bloodstream over two to five days. Improvements last only four to six weeks, although the treatment can be repeated. Despite its effectiveness and minimal side effects, the high expense of IVIg prevents it from becoming a standard initial treatment for PM or DM. Plasmapheresis is a blood-filtering procedure pioneered by MDA in the 1970s. It's occasionally used to treat PM or DM when other treatments don't work, but it has had greater success in another autoimmune disease, myasthenia gravis. Several other treatments are still considered experimental, and are likely to be offered only as a last resort. These include whole-body irradiation and removal of the thymus gland (thymectomy). How are the skin disorders of dermatomyositis treated? The DM rash usually improves with immunosuppressive treatment. For persistent rash, hydroxychloroquine may be effective. Topical corticosteroids may also be prescribed. Since the rash may worsen with sun exposure, avoidance of direct sunlight and use of sunscreen are recommended. The calcinosis seen most often in juvenile dermatomyositis is difficult to treat. Colchicine is the most commonly prescribed drug. Nodules that are accessible can be removed surgically, although the pain or disability caused by their presence must be weighed against the risk of infection from surgery. How can pain be treated? The most common treatments for pain are the non-steroidal anti-inflammatory drugs, or NSAIDS. These include aspirin, ibuprofen, acetaminophen and naprosyn. When these are inadequate, a codeine-based pain reliever may be prescribed. Many non-drug methods can also relieve pain, including hot baths, application of hot or cold packs, stretching or exercise. How can a person with PM or DM maintain and improve mobility? Regular stretching exercises, prescribed by a physical therapist, help to maintain the range of motion in weakened limbs. This prevents the development of contractures, or permanent muscle shortening. For people whose weakness limits their mobility, aids such as a cane, walker or wheelchair can increase their ability to remain mobile in the home, community or workplace. Braces for the legs, neck or wrist are also commonly used. An occupational therapist can recommend the type of device best suited to the needs of the person with PM or DM. How are swallowing difficulties treated? A speech therapist can evaluate swallowing difficulties, and may be able to recommend strategies to improve swallowing. Dietary changes or special food preparation techniques may be useful. In some cases, surgical removal of some muscle tissue in the throat (cricopharyngeal myotomy) can improve swallowing. If swallowing remains difficult and becomes unsafe (because of the risk of aspirating food into the lungs), a gastrostomy tube can be used to introduce food directly into the stomach. What treatments are used for other associated conditions? Interstitial lung disease is treated with the same range of immunosuppressive drugs as myositis is. The treatment of cancer depends on the type and location of tumor detected. What is the usual course of PM and DM? Studies have shown that prompt and aggressive treatment of PM and DM can help prevent worsening of the disease, and improve the prospects for recovery of strength. Early treatment of juvenile dermatomyositis may help prevent calcinosis. Most people with PM and DM respond well to treatment, especially if it's begun early. Nonetheless, there may be some residual weakness, and relapses do occur. Lifespan may be reduced in the presence of cancer, significant heart disease, dysphagia or interstitial lung disease. Pregnancy may be a special concern for a woman with PM or DM. Women with active disease may worsen during pregnancy, and are at increased risk for premature delivery or stillbirth. Women with their disease in remission during pregnancy often don't have flare-ups, and are more likely to have a successful pregnancy. Back to Disease Booklets