Clinical Heterogeneity of Interstitial Lung Disease in Polymyositis and Dermatomyositis Patients With or Without Specific Autoantibodies.

Background: The aim of this study was to compare the heterogeneity of interstitial lung disease (ILD) in patients with polymyositis and dermatomyositis (PM/DM) according to serological type.

Methods: A total of 182 patients with PM/DM-ILD were observed retrospectively. Antiaminoacyl-tRNA synthetase (ARS) and antimelanoma differentiation-associated gene5 (MDA5) antibodies were screened using immunoblotting approach. The patients with ILD were divided into 3 groups: MDA5 (with anti-MDA5 antibody), ARS (with anti-ARS antibody) and MSN (without anti-MDA5 or anti-ARS antibody) group. Pulmonary features, treatment responses and prognoses were compared among the groups.

Results: A higher percentage of rapidly progressive ILD (RP-ILD) occurrences (55.8% versus 25% versus 16.9%, P < 0.001) was observed in the MDA5 group compared to ARS and MSN groups. The MSN group experienced lower dyspnea (48.2% versus 79% versus 71.4%, P = 0.001) and fever (18.1% versus 39.5% versus 37.5%, P = 0.01) frequencies compared to MDA5 and ARS groups. Response to 6-month treatment among 95 patients showed highest deterioration ratio (70%, P = 0.001) of ILD in the MDA5 group. Additionally, the highest frequency of ILD improvement (60%, P = 0.04) was observed in the ARS group. During the observation period, 24 patients died of respiratory failure. The 5-year survival rates were significantly lower in MDA5 group (50.2%) compared to ARS group (97.7%) or the MSN group (91.4%) (P < 0.001).

Conclusions: MDA5-ILD was associated with severe pulmonary manifestations, poor response to treatment and aggravated prognosis. The ARS-ILD group had favorable treatment response and prognosis. MSN-ILD patients had relatively worse treatment response and prognosis compared to the ARS group, even though they expressed milder pulmonary manifestation.