Background/Purpose: Pneumomediastinum is an important complication in patients with myositis-associated interstitial lung disease (ILD). Patients with myositis and ILD who had pneumomediastinum during the disease course have a poor outcome, often fatal, especially in the case of rapidly-progressive ILD (RP-ILD). The purpose of this study was to establish the clinical features and risk factors for mortality in patients with myositis-associated ILD accompanied by pneumomediastinum.

Methods: Retrospective study of patients attending Tokai University Hospital between 2011 and 2020, with idiopathic inflammatory myopathies (IIMs) satisfying the ACR/EULAR classification criteria and with ILD diagnosed based on the clinical course of respiratory symptoms, function and computed tomography. Patients´ sera were screened for autoantibodies using protein immunoprecipitation assays. Clinical features and prognostic risk factors were compared between patients with or without pneumomediastinum using univariate and multivariate analyses and multiple logistic regression models.

Results: Of 164 patients with IIMs accompanied by ILD, 23 (12 female, 11 male; mean age 58.6, range 36-80 years) developed pneumomediastinum during their clinical course. Seven of these patients had classic dermatomyositis (DM) and 11 had clinically amyopathic DM (CADM), 3 had polymyositis (PM) and 2 had anti-aminoacyl-tRNA synthetase (ARS) antibody syndrome. Twelve possessed antibodies specific for melanoma differentiation-associated gene 5 (MDA5) and 8 had anti-ARS antibodies (3 with anti-PL-7, 3 with anti-EJ, and 2 with anti-PL-12 antibodies). Frequencies of smoking and anti-MDA5 antibody-positivity were significantly higher in patients with pneumomediastinum than in those without (61% vs. 36%, P=0.027; 52% vs. 20%, P=0.001, respectively). By univariate analysis, pneumomediastinum during the clinical course was identified as an initial factor associated with subsequent mortality due to ILD. However, multiple regression analysis revealed that anti-MDA5-positivity, but not pneumomediastinum during the clinical course, was an independent factor associated with mortality due to ILD (HR= 4.84, 95% CI: 2.3, 10.7, P=0.01; HR= 2.42, CI: 1.0, 5.4, P=0.11, respectively).

Conclusion: These results indicate that pneumomediastinum frequently coexists with anti-MDA5-positivity and that the presence of anti-MDA5 antibody might be a potential confounding factor for pneumomediastinum with regard to mortality due to ILD in patients with myositis-associated ILD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-pneumomediastinum-with-poor-prognosis-in-patients-with-myositis-associated-interstitial-lung-disease/