Acute exacerbation in fibrotic interstitial lung disease: an international working group report.

Acute exacerbations (AEs) occur both in patients with idiopathic pulmonary fibrosis (IPF) and those with non-IPF fibrotic interstitial lung disease (fILD). These events confer high morbidity and mortality, with a lack of proven effective therapeutic interventions. The objective of this state-of-the-art document is to summarize latest evidence since the 2016 International Working Group Report on AE-IPF, expanding it across the spectrum of all fILDs. A comprehensive literature review on the epidemiology, associated and risk factors, prognosis, and management of AE-fILD is summarized. In addition to revising the AE definition and diagnostic criteria for broad application across different fILDs, a conceptual framework for acute respiratory worsening (ARW) has been proposed to encompass a variety of acute respiratory deteriorations, both related and unrelated to AEs. This allows structured evaluation in both clinical and research settings. The proposed revised definition for AE-fILD is an acute respiratory event characterized by increased respiratory symptoms or signs and associated with radiologic or histologic features consistent with diffuse alveolar damage (with or without superimposed organizing pneumonia) in a patient with known or newly diagnosed fILD. On the other hand, ARW refers to a heterogeneous group of clinical events with acute symptom worsening not attributable to diffuse alveolar damage in patients with fILD, such as pulmonary edema, bronchitis, and pneumonia, although severe pneumonia can trigger AE-fILD. Additionally, we discuss considerations for inclusion of AE as a clinical trial endpoint, as well as research priorities for advancing knowledge on the pathogenic mechanisms, event prediction, risk stratification, and development of drugs and supportive treatments.