Inflammatory myopathy with cytochrome oxidase negative muscle fibers: Methotrexate treatment
✍ Scribed by Todd D. Levine; Alan Pestronk
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 123 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0148-639X
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✦ Synopsis
Inflammatory myopathy with cytochrome oxidase negative muscle fibers (IM/COX-) is characterized by slowly progressive weakness, most prominent in the quadriceps, muscle fibers with reduced COX staining and mitochondrial DNA mutations, and a poor response to corticosteroid treatment. We reviewed records of quantitative measurements of muscle strength in 7 IM/COX-patients to evaluate the outcomes after treatment with oral, once weekly, methotrexate for an average of 15 months. We compared the results to 6 patients with IM/COX-who received no long-term immunosuppression, and to 4 with inclusion body myositis (IBM) who received methotrexate during the same period. Methotrexate treatment of IM/ COX-was followed by improved muscle strength in 5 of 7 patients, averaging 17 ± 5%. In contrast, there was no improvement in the strength of 6 untreated IM/COX-patients (-6 ± 4%; P = 0.003), or 4 methotrexate-treated IBM patients (1 ± 2%; P = 0.03). We conclude that, despite clinical similarities to inclusion body myositis, which is usually refractory to immunosuppressive therapy, strength in IM/COX-appears to improve with methotrexate treatment. Biopsy studies of inflammatory myopathies with evaluation of muscle for mitochondrial changes and vacuoles can help to direct the choice of appropriate immunomodulating treatments.