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Myositis

The diseases dermatomyositis and polymyositis both involve myositis. Polymyositis causes muscle weakness, usually in the muscles closest to the trunk of your body. Dermatomyositis causes muscle weakness, plus a skin rash. Both diseases are usually treated with prednisone, a steroid medicine, and sometimes other medicines.

What is Dermatomyositis?

Dermatomyositis is one of a group of muscle diseases known as the inflammatory myopathies, which are characterized by chronic muscle inflammation accompanied by muscle weakness.Dermatomyositis’ cardinal symptom is a skin rash that precedes or accompanies progressive muscle weakness. The rash looks patchy, with bluish-purple or red discolorations, and characteristically develops on the eyelids and on muscles used to extend or straighten joints, including knuckles, elbows, heels, and toes. Red rashes may also occur on the face, neck, shoulders, upper chest, back, and other locations, and there may be swelling in the affected areas. The rash sometimes occurs without obvious muscle involvement. Adults with dermatomyositis may experience weight loss or a low-grade fever, have inflamed lungs, and be sensitive to light. Children and adults with dermatomyositis may develop calcium deposits, which appear as hard bumps under the skin or in the muscle (called calcinosis). Calcinosis most often occurs 1-3 years after the disease begins. These deposits are seen more often in children with dermatomyositis than in adults. In some cases of dermatomyositis, distal muscles (muscles located away from the trunk of the body, such as those in the forearms and around the ankles and wrists) may be affected as the disease progresses. Dermatomyositis may be associated with collagen-vascular or autoimmune diseases, such as lupus.



Is there any treatment?

There is no cure for dermatomyositis, but the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The standard treatment for dermatomyositis is a corticosteroid drug, given either in pill form or intravenously. Immunosuppressant drugs, such as azathioprine and methotrexate, may reduce inflammation in people who do not respond well to prednisone. Periodic treatment using intravenous immunoglobulin can also improve recovery. Other immunosuppressive agents used to treat the inflammation associated with dermatomyositis include cyclosporine A, cyclophosphamide, and tacrolimus. Physical therapy is usually recommended to prevent muscle atrophy and to regain muscle strength and range of motion. Many individuals with dermatomyositis may need a topical ointment, such as topical corticosteroids, for their skin disorder. They should wear a high-protection sunscreen and protective clothing. Surgery may be required to remove calcium deposits that cause nerve pain and recurrent infections.

What is the prognosis?

Most cases of dermatomyositis respond to therapy. The disease is usually more severe and resistant to therapy in individuals with cardiac or pulmonary problems.

What research is being done?

The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research relating to dermatomyositis in laboratories at the NIH and support additional research through grants to major medical institutions across the country. Currently funded research is exploring patterns of gene expression among the inflammatory myopathies, the role of viral infection as a precursor to the disorders, and the safety and efficacy of various treatment regimens.

What is Polymyositis?

Polymyositis is one of a group of muscle diseases known as the inflammatory myopathies, which are characterized by chronic muscle inflammation accompanied by muscle weakness. Polymyositis affects skeletal muscles (those involved with making movement) on both sides of the body. It is rarely seen in persons under age 18; most cases are in adults between the ages of 31 and 60. Slow, but progressive muscle weakness starts in the proximal muscles (muscles closest to the trunk of the body) which eventually leads to difficulties climbing stairs, rising from a sitting position, lifting objects, or reaching overhead. People with polymyositis may also experience arthritis, shortness of breath, difficulty swallowing and speaking, and heart arrhythmias. In some cases of polymyositis, distal muscles (muscles further away from the trunk of the body, such as those in the forearms and around the ankles and wrists) may be affected as the disease progresses. Polymyositis may be associated with collagen-vascular or autoimmune diseases, such as lupus. Polymyositis may also be associated with infectious disorders, such as HIV-AIDS.

Is there any treatment?

There is no cure for polymyositis, but the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The standard treatment for polymyositis is a corticosteroid drug, given either in pill form or intravenously. Immunosuppressant drugs, such as azathioprine and methotrexate, may reduce inflammation in people who do not respond well to prednisone. Periodic treatment using intravenous immunoglobulin can also improve recovery. Other immunosuppressive agents used to treat the inflammation associated with polymyositis include cyclosporine A, cyclophosphamide, and tacrolimus. Physical therapy is usually recommended to prevent muscle atrophy and to regain muscle strength and range of motion.

What is the prognosis?

The prognosis for polymyositis varies. Most people respond fairly well to therapy, but some have a more severe disease that does not respond adequately to therapies and are left with significant disability. In rare cases individuals with severe and progressive muscle weakness will develop respiratory failure or pneumonia. Difficulty swallowing may cause weight loss and malnutrition.

What research is being done?

The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research relating to polymyositis in laboratories at the NIH and support additional research through grants to major medical institutions across the country. Currently funded research is exploring patterns of gene expression among the inflammatory myopathies, the role of viral infection as a precursor to the disorders, and the safety and efficacy of various treatment regimens.