Myositis-associated Interstitial Lung Disease: Predictors of Failure of Conventional Treatment and Response to Tacrolimus in a US Cohort

Objective. Patients with myositis-associated interstitial lung disease (MA-ILD) are often refractory to conventional treatment, and predicting their response to therapy is challenging. Recent case reports and small series suggest that tacrolimus may be useful in refractory cases. Methods. A retrospective cohort study of patients with MA-ILD comparing clinical characteristics between those who responded to or failed conventional treatment. In those who failed conventional treatment and received adjunctive tacrolimus, response to tacrolimus was measured by the improvement in myositis, ILD, and change in the dose of glucocorticoids. Results. Thirty-one of 54 patients (57%) responded to conventional treatment based on the predefined variables of improvement in myositis and/or ILD. Patients with polymyositis (PM)-ILD were more likely to respond to conventional treatment than those with dermatomyositis (DM)-ILD (67% vs 35%, p = 0.013). Twenty-three patients failed conventional treatment, 18 of whom subsequently received adjunctive tacrolimus. Ninety-four percent had improvements in ILD and 72% showed improvement in both myositis and ILD. The mean doses of prednisone decreased from baseline by 65% at 3-6 months (p = 0.002) and 81% at 1 year (p < 0.001). Conclusion. Patients with PM-ILD were more likely to respond to conventional treatment than patients with DM-ILD, but clinical characteristics and serology did not otherwise predict response to therapy. A majority of patients with MA-ILD refractory to conventional therapy improved while receiving tacrolimus and were able to decrease their dose of both glucocorticoids and other disease-modifying antirheumatic drugs.