Polymyositis, dermatomyositis, and inclusion-body myositis
Article Abstract:
Inflammatory myopathies are conditions in which muscle weakness develops and cells typical of inflammation appear in muscle tissue. Three main types of inflammatory myopathy can be distinguished: polymyositis, dermatomyositis, and inclusion-body myositis. The clinical signs, diagnosis, pathogenesis, and treatment of these diseases are reviewed in this article. The incidence of all three disorders is approximately 1 in 100,000. Dermatomyositis affects people of any age, while polymyositis is rarely seen in children. All three disorders involve proximal muscle weakness (in muscles close to the trunk) that progresses slowly; typically, patients begin to notice difficulty in climbing steps or combing hair. Fine-motor problems, such as buttoning a shirt or writing, begin later in dermatomyositis and polymyositis and earlier in inclusion-body myositis. Dermatomyositis is characterized by a distinctive rash, while polymyositis is diagnosed by excluding other conditions. Inclusion-body myositis may be present when the distal muscles (that extend the foot or flex the fingers) become weak. Many patients with inflammatory myopathy develop difficulty in swallowing because of involvement of the throat and esophageal muscles. Symptoms can also involve the heart, lungs, skin, or joints. Diagnosis of the three disorders depends on tests that measure muscle enzyme levels in the blood; electromyography (recording the electrical impulses associated with muscle contraction); and muscle biopsy. It is likely that the disorders are of autoimmune origin (in which the body's immune system attacks its own proteins). The evidence for this is evaluated. Specific antigens have not been identified. Viruses may trigger the disorders, but their presence in muscle has not been documented. Treatment for polymyositis and dermatomyositis consists first of prednisone (a corticosteroid drug); if this is ineffective or associated with too many side effects, nonsteroidal immunosuppressive drugs may be used. Physical therapy should be started early in the course of the disease. Inclusion-body myositis usually resists treatment. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 1991
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Mitochondrial myopathy caused by long-term zidovudine therapy
Article Abstract:
Zidovudine, also called AZT, is used in the treatment of AIDS. Prior to the introduction of zidovudine treatment, a few AIDS patients developed myopathies (muscle disorders) of various descriptions, including inflammatory myopathy, noninflammatory destructive myopathy, and granular fiber degeneration. Recently an increasing number of AIDS patients taking zidovudine have developed myopathies which actually improve when the drug is discontinued. It seems, therefore, that there are some myopathies directly due to HIV infection and others due to zidovudine treatment. Since there has been no effective criterion for the clinical distinction between AIDS myopathy and zidovudine myopathy, the discontinuation of the drug in AIDS patients with myopathy has not been recommended. Now pathological changes have been observed in the muscle tissue of AIDS myopathy patients receiving zidovudine which are not seen in other AIDS myopathy cases. Under the light microscope, ''ragged-red'' muscle fibers may be seen using the Gomori trichrome stain. The extent of the fibers roughly correlates with the severity of the myopathy. This appearance of the muscle fibers is usually associated with mitochondrial abnormalities; this was confirmed by electron microscopy. Under EM, abnormal mitochondria, rod-like organelles inside the cell that are responsible for the cell's energy production, had rectangular and square-shaped paracrystalline inclusions; these inclusions were only observed in patients taking zidovudine. The authors suggest that AIDS patients with myopathy be first treated with a non-steroidal anti-inflammatory agent, with or without a reduction in zidovudine, as prednisone is potentially dangerous to AIDS patients. If this regimen does not work, zidovudine may be withheld and another antiviral agent substituted. If the patient's strength does not improve, zidovudine should be reinstituted. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 1990
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Desmin myopathy, a skeletal myopathy with cardiomyopathy caused by mutations in the desmin gene
Article Abstract:
Mutations in the gene for desmin can cause muscle diseases, including a disease of heart muscle called cardiomyopathy. Desmin is a protein that maintains the structural integrity of skeletal muscle and heart muscle. In some muscle diseases, desmin accumulates in abnormal amounts. These diseases are called desmin-related myopathies. In a study of 22 patients with desmin-related myopathy, 11 had a mutation in the gene for desmin. Six different mutations were identified. Seven patients with a desmin mutation also had cardiomyopathy.
Publication Name: The New England Journal of Medicine
Subject: Health
ISSN: 0028-4793
Year: 2000
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