Comparison of long-term prognosis and relapse of dermatomyositis complicated with interstitial pneumonia according to autoantibodies: anti-aminoacyl tRNA synthetase antibodies versus anti-melanoma differentiation-associated gene 5 antibody

The aim of this study was to investigate long-term prognosis and relapse of dermatomyositis complicated with interstitial pneumonia (DMIP) according to anti-aminoacyl tRNA synthetase (ARS) antibodies and anti-melanoma differentiation-associated gene 5 (MDA5) antibody. This retrospective study comprised 36 patients with DMIP who were divided into the anti-ARS antibody-positive group (ARS+) (n = 12), anti MDA5 antibody-positive group (MDA5+) (n = 11), double-negative group (ARS−/MDA5−) (n = 11), and double-positive group (ARS+/MDA5+) (n = 1). Clinical features, treatment, prognoses, and relapses during the 2 years after initiation of treatment were compared between three groups excluding ARS+/MDA5+ group. Although short-term (24-week) mortality in MDA+ was higher than that in ARS+ or ARS−/MDA5− (P = 0.004), there was no difference in long-term (2-year) mortality between the three groups. Relapse rate in ARS+ was higher than that in MDA5+ and ARS−/MDA5− during the 2 years after initiation of treatment (P = 0.044). There was no difference in serum KL-6 levels at the initiation of treatment between ARS+ and MDA5+, but serum ferritin levels in MDA5+ were significantly higher than those in ARS+ (P = 0.406, 0.042, respectively). Serum KL-6 and ferritin levels at 2 years after initiation of treatment in ARS+ were significantly higher than those in MDA5+ (P = 0.008, 0.034, respectively). We found that in MDA5+ DMIP, acute alveolar inflammation caused a poor prognosis early in the disease course, and in ARS+ DMIP, chronic injury to the alveolar epithelial cells or basement membrane caused long-term recurrence.