Pleural effusion as a predictor of rapidly progressive interstitial lung disease and mortality in idiopathic inflammatory myopathies.

Objectives: This study aimed to evaluate the clinical significance of pleural effusion in adult patients with idiopathic inflammatory myopathies (IIM).

Methods: We assessed a cohort of 158 consecutive patients with IIM. Clinical features and survival rates were compared between patients with and without pleural effusion.

Results: Of those 158 IIM patients, 28 (17.7%) developed pleural effusion. 125 (79.1%) IIM patients had interstitial lung disease (ILD), 26 (20.8%) of which developed pleural effusion. Notably, pleural effusion was associated with a higher incidence of lower lung zone consolidation, rapidly progressive ILD (RP-ILD) and elevated high-resolution computed tomography (HRCT) score, and could robustly predict RP-ILD independently [HR 7.863 (2.160-28.617), p=0.002] in IIM-ILD patients. IIM patients with pleural effusion presented with increased systemic inflammatory response, including more fever, elevated white blood cell count, neutrophil/lymphocyte ratio, C-reactive protein, and erythrocyte sedimentation rate, alongside reduced lymphocyte percentage. Pleural effusion was also associated with more ILD, lower lung zone consolidation, pericardial effusion and RP-ILD, higher HRCT score, and lower HB and albumin levels in IIM. Except for neutrophil/lymphocyte ratio, ILD and pericardial effusion, other correlative variables were potential predictors of higher mortality in IIM. Furthermore, pleural effusion remained an independent predictor of higher mortality in IIM [HR 5.05 (1.633-15.62), p=0.005].

Conclusions: Pleural effusion showed a significant positive association with severe phenotypes of ILD and was the powerful predictor of RP-ILD in IIM-ILD. Furthermore, pleural effusion could reveal adverse disease phenotypes with higher systemic inflammatory level and predict higher mortality independently in IIM.