Spontaneous pneumomediastinum and/or pneumothorax in anti-MDA5 dermatomyositis: a refined staging system

BACKGROUND: Spontaneous pneumomediastinum and/or pneumothorax (SPM/P) have been Linked to unfavorable outcome in anti-melanoma differentiation-associated gene 5 positive dermatomyositis (MDA5+DM) patients. This study attempted to investigate the prognostic value of SPM/P and identify the predisposing factors of SPM/P in patients with interstitial lung disease (ILD) complicated with MDA5+DM. METHODS: This study was conducted in a large inception cohort of MDA5+DM-ILD (from 2014 to 2023) at Shanghai Renji Hospital. Baseline demographic data, pulmonary function tests, high-resolution CT imaging, laboratory parameters and survival status within 12 months were collected and compared between survivors and deceased patients, as well as between patients with and without SPM/P. Kaplan–Meier curves were plotted and Cox regression models were applied to identify prognostic factors. Furthermore, logistic regression analysis was employed to determine the predictors of SPM/P development. RESULTS: In a cohort of 523 MDA5+DM-ILD patients, 92 (17.6%) developed SPM/P. Of those, 63 SPM/P cases occurred within 3 months since ILD onset and had a significantly higher 12-month mortality than those without SPM/P (82.5% versus. 35.4%, p < 0.001). Multivariable Cox regression model identified SPM/P occurred within 3 months as an independent risk factor for survival (HR 1.59, 95% CI 1.09–2.34, P = 0.018). Predisposing factors for SPM/P included severe restrictive ventilation dysfunction, male sex, and CMV viremia. CONCLUSIONS: SPM/P occurred within 3 months since ILD onset was identified as a poor prognostic factor in MDA5+DM-ILD. A refined FVC%-based staging system combining SPM/P was proposed for better risk stratification and to gauge clinical trial design.