Clinical Characteristics of and Risk Factors for Interstitial Lung Disease, Other Rheumatic Diseases and Malignancy in Adult Polymyositis and Dermatomyositis: A Retrospective Cohort Study

Objectives: To identify the clinical characteristics of patients with idiopathic inflammatory myopathies(IIMs), including adult polymyositis(PM) and dermatomyositis(DM), and to assess their risk factors for interstitial lung disease(ILD), other rheumatic diseases and malignancy in these patients Methods: A retrospective cohort study was conducted. The clinical characteristics of 397 patients with IIMs who visited Nanfang Hospital in China during 2016-2019 were recorded. Continuous and frequency data were analysed. Bivariate associations between the clinical characteristics of patients and risk factors for ILD, other rheumatic diseases and malignancy were analysed. Logistic regression analysis was used to identify the effect of each potential risk factor in the model. Results: A total of 119 patients with PM and 191 patients with DM were included. A variety of skin or muscle involvements, arthralgia, Raynaud's phenomenon, ILD, overlapping other rheumatic diseases and malignancy were common. The anti-PM/Scl (AOR=4.779,95%CI1.486-15.363), anti-Ro52 (AOR=1.917,95%CI1.173-3.132), anti-aminoacyl-tRNA synthetase (AOR=5.092,95%CI1.189-21.795) and anti-MDA5 (AOR=7.714,95%CI1.649-36.085) antibodies were risk factors for ILD (all p<0.05), whereas overlapping malignancy was a protective factor (AOR=0.107,95%CI0.027-0.430,p=0.002) for ILD across all groups. In different subgroup models, Raynaud's phenomenon (AOR=51.233,95%CI2.644-992.614), arthralgia (AOR=4.261,95%CI1.169-15.531) and semi-quantitative anti-nuclear antibody (AOR=3.047,95%CI1.132-8.205; all p<0.05) were risks factors for other overlapping rheumatic diseases. Male sex (AOR=2.533,95%CI1.014-6.330) and anti-TIF1γ antibodies (AOR=16.949,95%CI3.350-85.739;all p<0.05) were risk factors, whereas disease duration (AOR=0.954,95%CI0.916-0.994) and combination of ILD (AOR=0.106;95%CI0.032-0.356;all p<0.05) were protective factors for overlapping malignancy in the total myositis group. Anti-NXP2 antibodies were identified as a risk factor for overlapping malignancy in patients with PM (AOR=73.152,95%CI1.274-4198.774,p=0.038). Conclusions: It is common for patients with PM and DM to have ILD, other rheumatic diseases or malignancy. Organ involvement and complications of these conditions are closely associated with the clinical manifestation of IIM as well as with myositis-specific or myositis-associated autoantibodies. Funding Statement: This study was supported by the Natural Science Foundation of China (No. 81803932) and the Natural Science Foundation of Guangdong Province (No. 2018030310025 and 2017A030313868). Declaration of Interests: All authors have declared that no conflict of interest exists. Ethics Approval Statement: The study was conducted according to the principles expressed in the Declaration of Helsinki. All patients had provided consent forms, which were approved by the Institutional Medical Ethics Review Board of Nanfang Hospital (29160510).