Clinical characteristics of patients with anti-aminoacyl-tRNA synthetase antibody positive idiopathic interstitial pneumonia

Background: Anti-aminoacyl-tRNA synthetase (ARS)antibodies have been detected in patients with polymyositis/ dermatomyositis (PM/DM)and are especially correlated with interstitial lung disease (ILD). The aim of this study was to clarify the clinical features of patients with anti-ARS antibody positive idiopathic interstitial pneumonias (IIPs). Methods: Patients were classified into three groups: 1) IIP with anti-ARS antibodies (ARS(+)IIP), 2)IIP without anti-ARS antibodies (ARS(-)IIP), and 3) PM/DM-associated ILD with anti-ARS antibodies (ARS(+)PM/DMILD). Clinical characteristics were compared retrospectively between the ARS(+)IIP group and the ARS(-)IIP group or ARS(+)PM/DM-ILD group. Results: Eighteen ARS(+)IIP, 284 ARS(-)IIP, and 20 ARS(+)PM/DM-ILD patients were enrolled. The ARS(+) IIP group was significantly older and the male sex was predominant, had a lower prevalence of signs of connective tissue disease, differences in HRCT findings and patterns, and higher KL-6 levels compared to the ARS (+)PM/DM-ILD group. The findings in the bronchoalveolar lavage fluid (BALF)showing lymphocytosis and a lower CD4/CD8 ratio were similar between the two groups. However, the ARS(+)IIP group had significantly lower percentage of sputum, higher prevalence of mechanic's hand, higher KL-6 levels, lower percentage of vital capacity in the pulmonary function test, and lower CD4/CD8 ratio in BALF, compared to the ARS(-)IIP group. Conclusions: The present study demonstrated that features of pulmonary involvement were similar to those in the ARS(+)PM/DM-ILD group; however, some differences including HRCT findings and higher KL-6 levels suggest that ARS(+)IIP has severe ILD compared with ARS(+)PM/DM-ILD. Further prospective studies with a larger number of patients will elucidate the exact role of anti-ARS antibodies in IIPs.