LCN2 and idiopathic pulmonary fibrosis: Recurrent epithelial damage is considered the initiating insult of IPF pathogenesis, and acute exacerbation of IPF is characterized by increased alveolar epithelial cell injury, suggesting that future studies on LCN2 and IPF should include the evaluation of LCN2 levels in patients with acute IPF exacerbation and the correlation with other epithelial injury markers.