Interstitial lung diseases are commonly caused by the following: 1. long-term inhalation of inorganic dust, such as working in coal mines; exposure to asbestos; inhalation of harmful gases; 2. inhalation of organic dust, such as farming mushrooms, keeping pets (such as pigeons, parrots, etc.), exposure to moldy grains, hay, etc.; contamination of air conditioners or humidifiers; 3. long-term use of the following drugs: such as amiodarone, methotrexate, chemotherapy drugs, etc.; 4. Chronic pulmonary infections: such as hematogenous tuberculosis, Pneumocystis carinii pneumonia, viral pneumonia, etc.; 5. Interstitial pulmonary edema due to chronic heart disease; 6. Interstitial pneumonia associated with autoimmune diseases such as rheumatoid arthritis, dry syndrome, polymyositis, systemic lupus erythematosus, scleroderma, and vasculitis; 7. Tumor-related, such as alveolar carcinoma, carcinomatous lymphangitis, lymphoma, etc.; 8. Most patients with pulmonary fibrosis have an unknown etiology. Among pulmonary fibrosis of unknown cause, the most common are idiopathic interstitial pneumonia, including idiopathic pulmonary fibrosis (abbreviated as IPF), cryptogenic mechanized pneumonia (COP), nonspecific interstitial pneumonia (NSIP), desquamative interstitial pneumonia (DIP), respiratory fine bronchiectasis interstitial lung disease (RB-ILD), lymphocytic interstitial pneumonia (LIP) and acute interstitial pneumonia (AIP), the most common of which is idiopathic pulmonary fibrosis. The term “idiopathic” means “of unknown etiology”.