Treatment of adult idiopathic inflammatory myopathies with conventional immunosuppressive drugs

To gain information about the efficacy of immunosuppressive drugs as first-, second-, and third-line treatment of idiopathic inflammatory myopathies (IIM).

112 treatment cycles of 63 patients with dermatomyositis (n = 23), polymyositis (n = 33), overlap syndromes (n = 4), and undifferentiated connective tissue diseases (n = 3) were analyzed by retrospective chart analysis. Data regarding muscle strength, muscle enzymes, treatment duration, and treatment discontinuation were collected.

Azathioprine (38 cycles) and methotrexate (MTX; 24 cycles) were applied significantly longer than glucocorticoid monotherapy (9 cycles; 25 ± 21, 26 ± 29 and 7 ± 4 months, respectively; p < 0.05). MTX and azathioprine achieved a significant reduction of serum creatine kinase (CK), with MTX showing more marked effects. Treatment cycles with immunosuppressants other than MTX or azathioprine (n = 22) or with combinations of immunosuppressive drugs (n = 19) were mostly applied as third-line therapy, indicating their application in more refractory cases. Significant improvement of muscle strength was confined to MTX and azathioprine and to the first-line treatment. 8% of MTX patients withdrew due to the lack of efficacy, compared with 29% of patients taking azathioprine and 6 of 9 patients taking glucocorticoid monotherapy. In the 12 patients with Jo-1 syndrome, MTX treatment was effective for a longer time than azathioprine (44 ± 21 months vs. 27 ± 24 months, p < 0.05).

Our data confirm the effectiveness of MTX and azathioprine in the treatment of inflammatory myopathies and stress the importance of a potent first-line therapy.