Fibrotic idiopathic interstitial lung disease: the molecular and cellular key players.

Interstitial lung disease (ILDs) that are known as diffuse parenchymal lung diseases (DPLDs) lead to the damage of alveolar epithelium and lung parenchyma culminating into inflammation and widespread fibrosis. ILDs that account for more than 200 different pathologies, can be di-vided into two groups: ILDs that have a known cause and those where the cause is unknown clas-sified as Idiopathic Interstitial Pneumonia (IIPs). IIPs include idiopathic pulmonary fibrosis (IPF), non-specific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia (COP) known also as bronchiolitis obliterans organizing pneumonia (BOOP), Acute interstitial pneumonia (AIP), Desquamative Interstitial Pneumonia (DIP), Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), and lymphocytic interstitial pneumonia (LIP). In this review our aim is to de-scribe the pathogenic mechanisms that lead to the onset and progression of the different IIPs, starting from IPF as the most studied, in order to find both common and standalone molecular and cellular key players among them. Finally, a deeper molecular and cellular characterization of different interstitial lung disease without known cause, would contribute to give a more accurate diagnosis to the patients, that would translate in a more effective treatment decision.