Patients older than age 40, particularly those with dermatomyositis, should be followed closely for the possibility of malignant disease. If a malignant lesion is found, it should be treated, since the muscle weakness may disappear if the neoplasm is eradicated. However, a response to glucocorticoids can usually be obtained even in patients with dermatomyositis-polymyositis associated with a malignancy.
Monitoring serum CK levels during reduction of immunosuppressive therapy is useful, since a rise in level generally indicates an incipient clinical relapse. CK levels are not used to monitor initial response to prednisone, because prednisone reduces CK levels independent of any effects on the disease process.
Side effects of high-dose daily glucocorticoid therapy are relatively common in patients treated for polymyositis and may limit therapy. However, these can be minimized by appropriate use of alternate-day therapy and judicious use of calcium supplements, vitamin D, and H2-receptor blockers. When patients who have been stable on a static dose of prednisone develop increasing muscle weakness, this may be due to either a relapse of the myositis or to glucocorticoid myopathy. An EMG, serum CK measurement, and, rarely, muscle biopsy may help in differentiating these two conditions if the changes of myositis are present. Often, however, the only way to distinguish between these two conditions is to reduce the dose of prednisone slowly; if glucocorticoid myopathy is the cause of the weakness, it will improve as the dose is reduced; if a relapse of the myositis is responsible, the weakness will increase with reduction in the dose.
Side effects of cytotoxic drugs include marrow suppression, alopecia, gastrointestinal tract disorders, damage to the testes and ovaries, infections, and potential for malignancy.
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