Effects of tacrolimus on dermatomyositis and polymyositis: a prospective, open, non-randomized study of nine patients and a review of the literature.

Dermatomyositis (DM) and polymyositis (PM) are often refractory to conventional therapy with corticosteroids sometimes combined with immune-suppressing agents and can lead to severe disability if these treatments are unsuccessful. In this prospective, open, non-randomized study, we examined the efficacy of tacrolimus (FK506), an immunosuppressant, in nine patients with DM (n = 5) or PM (n = 4) who did not respond to previous therapy. Outcomes included compound muscle strength, ambulatory status, and serum creatine kinase activity measured at intervals after starting tacrolimus. At 6 months after the introduction of tacrolimus, all five patients with DM and three patients with PM showed clinical improvements. Patients with a disease duration of <4 years and those with trough level of tacrolimus >5 ng/ml tended to have better outcomes than those with longer disease duration or lower trough levels. There were no side effects other than moderate hypertension and aggravation of diabetes mellitus. Tacrolimus was beneficial in the majority of patients with PM or DM refractory to corticosteroid therapy. It was also effective in four patients who were previously treated with other immunosuppressants or intravenous immunoglobulin combined with corticosteroids. These results warrant further studies as to the efficacy of tacrolimus compared to other immunosuppressing agents.