LAUSR

OBJECTIVE Mortality of dermatomyositis patients positive with anti-melanoma differentiation-related gene 5 antibody (anti-MDA5-DM) is alarming, especially during the first several months. Infection is an important cause of early death. As there are no reports regarding the effect of prophylactic use of the compound sulfamethoxazole (SMZ Co) on anti-MDA5-DM patients, we conducted this study to evaluate the efficacy of SMZ Co in reducing the incidence of pneumocystis jirovecii pneumonia (PJP). METHOD Consecutive patients with newly onset anti-MDA5-DM from June 2018 to October 2021 in our center were retrospectively reviewed for over 12 months. They were divided into two groups: SMZ Co and non-SMZ Co groups based on the initial use of prophylactic SMZ Co. Mortality and incidence of severe infection within 12 months were compared between two groups. RESULTS . Compared with the non-SMZ Co group (n = 93), the SMZ Co group (n = 121) had lower mortality (18.8% vs 51.1%; p＜ 0.001), and lower incidence of PJP (6.8% vs 15.2%; p= 0.040) and fatal infection (16.1% vs 3.3%; p= 0.001) during the first 12 months from diagnosis. After adjusting for age, gender, disease duration, peripheral blood lymphocyte count, anti-MDA5-Ab titers, GGO scores, and treatments, an inverse association was revealed between the prophylactic use of SMZ Co and incidence of PJP (adjusted OR : 0.299; 95% CI, 0.102-0.878, p= 0.028). CONCLUSIONS Prophylactic use of SMZ Co is an effective and safe way to improve the prognosis of anti-MDA5-DM patients by preventing the incidence of PJP.