# The Clinical Features and Prognosis of Idiopathic and Infection-Triggered Acute Exacerbation of Idiopathic Inflammatory Myopathy-Associated Interstitial Lung Disease: A Preliminary Study

## TL;DR

This study compares the clinical features and outcomes of two types of acute exacerbations in lung disease linked to muscle inflammation, finding that infection-triggered cases are more severe and deadly.

## Contribution

The study identifies distinct clinical and radiological features that differentiate infection-triggered from idiopathic acute exacerbations in IIM-ILD.

## Key findings

- Infection-triggered AE showed more severe inflammation and worse survival compared to idiopathic AE.
- Higher mortality rates were observed in infection-triggered AE at 30, 90 days, and 1 year.
- Combining NEU and GGO extent improved differentiation between AE subtypes with good accuracy.

## Abstract

Background: Acute exacerbation (AE) of idiopathic inflammatory myopathy-associated interstitial lung disease (IIM-ILD) is fatal. Infection is one of the most important triggers of the AE of IIM-ILD. We evaluated the clinical features and prognosis of idiopathic (I-AE) and infection-triggered (iT-AE) acute exacerbation in IIM-ILD patients. Methods: We retrospectively reviewed 278 consecutive patients with IIM admitted to our hospital between January 2014 and December 2020. Among them, 69 patients experienced AE of IIM-ILD, including 34 with I-AE and 35 with iT-AE. Clinical features and short- and long-term outcomes were analyzed in this preliminary study. Results: Compared with I-AE, patients with iT-AE presented with lower hemoglobin and PaO2/FiO2 ratios but higher pulse, body temperature, white blood cell count, neutrophil percentage (NEU), C-reactive protein, erythrocyte sedimentation rates, lactate dehydrogenase, and hydroxybutyrate dehydrogenase levels. They also had more extensive ground-glass opacities (GGOs) on high-resolution computed tomography (all p < 0.05). Mortality was significantly higher in iT-AE than that in I-AE at 30 days (28.6% vs. 5.9%), 90 days (34.3% vs. 14.9%), and 1 year (54.3% vs. 17.6%; log-rank test, p = 0.002). Multivariate logistic regression showed that the combination of NEU and GGO extent could help discriminate iT-AE from I-AE (area under the receiver operating characteristic curve: 0.812; 95% confidence interval: 0.711–0.913; sensitivity: 71.4%, specificity: 73.5%, accuracy: 72.5%). Conclusion: This study found that iT-AE patients exhibited more severe hyperinflammation and markedly worse survival than I-AE patients. Combining NEU and GGO extent may assist in differentiating AE subtypes. Larger prospective studies are required to validate these findings.