Definition:

Idiopathic interstitial pneumonias (IIP) are a heterogeneous subset of interstitial lung diseases, characterized by unknown aetiology. Despite the varied nature of IIPs, the common histological feature is distortion of lung interstitium by highly variable combinations of inflammation and fibrosis. Patients experience common symptoms related to their chronic lung disease. Dyspnoea, cough, fatigue and depression contribute substantially to morbidity and are often difficult to manage. It has been reported that pulmonary rehabilitation plays a central role in symptom management and has beneficial effects. According to the current American thoracic society/European respiratory society (ATS/ERS), IIPs are categorised as major IIPs, rare IIPs and unclassifiable IIPs. There are six major IIPs, namely, idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia (NSIP), respiratory bronchiolitis-interstitial lung disease (RB-ILD), desquamative interstitial pneumonia (DIP), cryptogenic organizing pneumonia (COP), and acute interstitial pneumonia (AIP). And they are divided into three major groups; chronic fibrosing IIP (IPF, NSIP), smoking-related IIP (RB-ILD, DIP), and acute/ subacute IIP (COP, AIP). The rare IIPs include idiopathic lymphoid interstitial pneumonia (LIP) and idiopathic pleuroparenchymal fibroelastosis. IPF accounts for the majority of IIP. It is considered to be lethal because prognosis is very poor and far worse than other types of IIP. An early and accurate diagnosis of IPF is critical.