BACKGROUND: Idiopathic pleuroparenchymal fibroelastosis (iPPFE) is a distinctive chronic interstitial lung disease characterized by upper lobe-dominant elastofibrosis. Deepening of the suprasternal notch is a notable physical feature in patients with iPPFE. However, the anatomical explanation and clinical significance of iPPFE have not yet been studied in detail. METHODS: We retrospectively examined 84 patients with iPPFE, 59 with idiopathic pulmonary fibrosis (IPF), 32 with chronic hypersensitivity pneumonitis (CHP), and 91 non-interstitial lung disease (ILD) controls. The depth of the suprasternal notch assessed on axial chest computed tomography and its association with clinical, radiological, and physiological parameters, and patient outcomes were investigated. RESULTS: The depth of the suprasternal notch was anatomically correlated with the thickness of the pre-tracheal soft tissue and posterior or right deviation of the trachea in patients with iPPFE. The depth of the suprasternal notch effectively discriminated patients with iPPFE from those with IPF (sensitivity, 75 %
specificity, 86.4 %), CHP (sensitivity, 75 %
specificity, 84.4 %), and non-ILD controls (sensitivity, 75 %
specificity, 83.5 %), with a cutoff value of 9.5 mm. A log-rank test showed that patients with iPPFE with a deep suprasternal notch had significantly shorter survival than those without a deep suprasternal notch. In addition, a multivariate Cox regression analysis adjusted for age, sex, and %forced vital capacity showed that the depth of the suprasternal notch was an independent risk factor for mortality. CONCLUSION: The suprasternal notch is a simple and useful indicator with diagnostic and prognostic implications for patients with iPPFE.