Pulmonary fibrosis (PF) is defined as a specific form of chronic fibrosing interstitial pneumonia that is limited to the lung and associated with the histological appearance of UIP on a surgical lung biopsy. The diagnosis of IPF can only be made after the exclusion of other known causes of interstitial lung disease such as drug toxicities, environmental exposures, and collagen vascular diseases.ILD is a collection of non-neoplastic lung disorders, both acute and chronic, that present with variable degrees of inflammation and fibrosis. ILD is also termed diffuse parenchymal lung diseases (DPLD(.The IIPs are defined by the ATS/ERS consensus classification as seven distinct disease entities. IPF is the most common IIP and its diagnosis is reserved for patients whose biopsy reveals the UIP pathology or in whom the clinical presentation and high-resolution computed tomography (HRCT) reveal a characteristic pattern.