Background Polymyositis (PM)/dermatomyositis (DM) are characterized by a systemic inflammation of a proximal skeletal muscles and/or a skin. Interstitial lung disease (ILD) is a common but life-threatening complication with PM/DM and often recurs despite intensive induction therapy. However, risk factors for the ILD flare are not determined.
Objectives To identify risk factors of the recurrence of PM/DM-ILD.
Methods Consecutive patients with PM/DM-ILD treated in our institution from 2002 to 2015 were enrolled in the study. The patients were divided into two groups according to the presence or absence of recurrence of ILD after the improvement by induction therapy; the recurrence group and the non-recurrence group. The patients were observed until the recurrence or the last visit to our clinic. The patients' characteristics and treatment between the two groups were compared.
Results A total of forty four patients with PM/DM-ILD underwent induction therapy. After excluding 1 deceased patient (induction failure) and 1 lost to follow-up, forty five PM/DM-ILD cases who had been treated with predonisolone (PSL) and/or immunosuppressive agents as induction therapy were included in the analysis. Recurrence occurred in 17 cases (37.8%). The mean duration from the time of induction therapy to the recurrence was 124 (42.5–241.0) weeks. The following period was 338.5 (166.3–777.5) weeks in the non-recurrence group. At the time of induction therapy, no difference was found between the recurrence group and the non-recurrence group in the mean age (47.6±14.3 vs 47.8±11.9 years, P=0.95), the male ratio (23.5% vs 30.8%, P=0.54), and the proportion of DM (64.7% vs 78.6%, P=0.31), respectively. The levels of C-reactive protein, lactate dehydrogenase and KL-6 were also not different. The percentage of vital capacity (%VC) in the recurrence group was lower than that of the non- recurrence group (59.6% vs 78.3%, P=0.004). The induction therapy regimen was not different between the 2 groups; glucocorticoid pulse, 17.6% vs 21.4% (P=0.84), the initial PSL dose, 0.87 mg/kg vs 0.89 mg/kg (P=0.17), the concomitant use of immunosuppressive agents including cyclophosphamide and/or calcineurine inhibitor with PSL, 47.1% vs 50.0% (P=0.85), in the recurrence and the non-recurrence group, respectively. The PSL dose was 8.3 mg at the recurrence in the recurrence group, and 7.9 mg at the last observation in the non-recurrence group (P=0.40). Immunosuppressive agent was more frequently used as maintenance therapy in the non-recurrence group than the recurrence group (89.3% vs 64.7%, P=0.047).
Conclusions PM/DM-ILD patients with low %VC at the induction therapy are inclined to recur. The concomitant use of immunosuppressive agent as maintenance after induction is important to prevent the recurrence of PM/DM-ILD. The study can improve the management of the PM/DM-ILD.
Disclosure of Interest None declared