Pulmonary fibrosis is a respiratory condition characterized by scarring of lungs and is a result of inflammatory process occurring inside the lungs. This process can occurs secondary to infections, autoimmune disorders or can be due to unknown reasons (idiopathic). The ongoing inflammatory process results in epithelial damage along with alveolar-capillary basement membrane destruction. This result in excessive deposition of collagen and extracellular matrix components due to the activation of myofibroblasts. CAUSES OF FIBROSIS Upper zone Fibrosis- mnemonic SCHART S- Silicosis, sarcoidosis C- Coal worker pneumoconiosis H- Histiocytosis (Langerhan cells histiocytosis) and histoplasmosis A- Allergic bronchopulmonary aspergillosis, Ankylosing spondylitis R- Radiation T- Tuberculosis Lower zone fibrosis- mnemonic RASCIO R- Rheumatoid arthritis A- Asbestosis S- Scleroderma C- Collagen vascular disease I- Idiopathic pulmonary fibrosis O- Others (Drugs bleomycin, nitrofurantoin, methotrexate, etc)