Abstract
The latest clinical practice guidelines for idiopathic pulmonary fibrosis (IPF) and progressive pulmonary fibrosis (PPF) were jointly published by the American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS), and Asociacion Latinoamericana de Thorax (ALAT) in 2022, and a new term-"PPF"-has been proposed to describe patients with non-IPF fibrosing interstitial lung diseases (ILDs), with defined criteria. However, the proposal of this new term has caused confusion amongst experts at a time when use of the term "progressive fibrosing interstitial lung disease" (PF-ILD), proposed in the phase 3 INBUILD trial of nintedanib, has become widely adopted by pulmonologists and rheumatologists in clinical practice. In this commentary, we discuss the background and concepts underpinning the terms PPF and PF-ILD and seek to provide pulmonologists and rheumatologists with a deeper understanding of the concept of PPF.