Idiopathic pulmonary fibrosis: pathogenesis and management

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease characterized by the aberrant accumulation of fibrotic tissue in the lungs parenchyma, associated with significant morbidity and poor prognosis. This review will present the substantial advances achieved in the understanding of IPF pathogenesis and in the therapeutic options that can be offered to patients, and will address the issues regarding diagnosis and management that are still open.

Main body: Over the last two decades much has been clarified about the pathogenic pathways underlying the development and progression of the lung scarring in IPF. Sustained alveolar epithelial micro-injury and activation has been recognised as the trigger of several biological events of disordered repair occurring in genetically susceptible ageing individuals. Despite multidisciplinary team discussion has demonstrated to increase diagnostic accuracy, patients can still remain unclassified when the current diagnostic criteria are strictly applied, requiring the identification of a Usual Interstitial Pattern either on high-resolution computed tomography scan or lung biopsy. Outstanding achievements have been made in the management of these patients, as nintedanib and pirfenidone consistently proved to reduce the rate of progression of the fibrotic process. However, many uncertainties still lie in the correct use of these drugs, ranging from the initial choice of the drug, the appropriate timing for treatment and the benefit-risk ratio of a combined treatment regimen. Several novel compounds are being developed in the perspective of a more targeted therapeutic approach; in the meantime, the supportive care of these patients and their carers should be appropriately prioritized, and greater efforts should be made toward the prompt identification and management of relevant comorbidities.

Conclusions: Building on the advances in the understanding of IPF pathobiology, the further investigation of the role of gene variants, epigenetic alterations and other molecular biomarkers reflecting disease activity and behaviour will hopefully enable earlier and more confident diagnosis, improve disease phenotyping and support the development of novel agents for personalized treatment of IPF.

Keywords: Diagnosis; Idiopathic pulmonary fibrosis; Interstitial lung disease; Management; Nintedanib; Pathogenesis; Pirfenidone; Treatment.

Fig. 1

Schematic view of IPF pathogenesis. Repeated injuries over time lead to maladaptive repair process, characterized by AEC2s apoptosis, proliferation and epithelium-mesenchymal cross-talk (a) and following fibroblasts, myofibroblasts proliferation and accumulation of extracellular matrix (b).CCL2: chemokine C-C motif ligand 2; CXCL12: C-X-C motif chemokine 12; FGF: fibroblast growth factor; PAI-1: plasminogen activator inhibitor 1; PAI-2: plasminogen activator inhibitor 2; PDGF: platelet-derived growth factor; TGF-β1: Transforming Growth Factor-Beta 1; TNF-α: tumor necrosis factor-alpha; VEGF: vascular endothelial growth factor

Fig. 2

Typical Usual Interstitial Pneumonia pattern on high resolution computed scan sections showing upper, middle and lower lung regions from left to right. Black arrows indicate subpleural honeycombing; white arrow indicates traction bronchiectasis