When it comes to “interstitial lung disease”, many patients and even medical professionals are still quite unfamiliar with this group of diseases. So, what is interstitial lung disease? Interstitial lung disease is a general term for a group of diffuse lung diseases characterized by inflammation and fibrosis of the alveolar wall, alveoli, and loose connective tissue around blood vessels and lymphatic vessels, with progressively increasing dyspnea as the main clinical manifestation. In other words, there is widespread inflammation and fibrosis of the basic respiratory units of the lung. Interstitial lung diseases include more than 200 different diseases with diverse and varied etiologies and complex pathogenesis. Therefore, interstitial lung diseases are often referred to as “difficult diseases” by patients, and are among the most challenging diseases to diagnose and treat in the respiratory system. In recent years, with the widespread use of diagnostic techniques such as high-resolution CT of the chest and bronchoalveolar lavage cytometry, the understanding of these diseases has been greatly improved. The occurrence of interstitial lung diseases is often related to occupational and environmental factors. Inhalation of inorganic dust due to occupational factors can lead to coal workers’ pneumoconiosis, asbestosis, silicosis, etc., while inhalation of organic dust may cause an immune response in the lungs leading to allergic pneumonia, such as “bird feeder’s lung” from keeping pigeons and parrots, “mushroom worker’s lung” from growing mushrooms “Inhalation of moldy cereals with thermophilic actinomycetes, microscopic polyspora, and heat-absorbing streptomycetes can cause “farmer’s lung”, and long-term air conditioning in contaminated rooms can cause “air conditioner’s lung”. Therefore, paying attention to occupational and environmental factors, strengthening occupational protection measures, and avoiding environmental risk factors can prevent the occurrence of some interstitial lung diseases. Some drugs and treatments can also cause interstitial lung disease, such as immunosuppressive drugs, chemotherapeutic drugs and biological agents. Radiotherapy to the chest can cause radiation pneumonia. Doctors will weigh the pros and cons of the condition to develop a treatment plan for the patient. When patients find interstitial lung damage, they should be screened for each drug they have been taking for a long time. Autoimmune diseases often involve multiple systems and organs, and their lung involvement usually manifests as interstitial lung disease. In some patients, the diagnosis of interstitial lung disease is accompanied by the detection of connective tissue diseases such as rheumatoid arthritis, polymyositis, or systemic sclerosis upon examination. Therefore, patients with autoimmune diseases, especially connective tissue diseases, should be concerned about interstitial lung damage. Some of the interstitial lung diseases have no known cause and are referred to as “idiopathic”. For example, idiopathic pulmonary fibrosis is a chronic fibrotic lung disease that develops in middle-aged and older adults, especially in those over 75 years of age. Patients with idiopathic pulmonary fibrosis have a poor prognosis, with a median survival time of less than 3 years, and current treatments have not yet been able to halt the progression of this lethal disease. Many basic and clinical studies are underway in the hope of developing new drugs to treat pulmonary fibrosis. In addition, there are many other types of interstitial lung diseases such as nodular disease, pulmonary vasculitis, amyloidosis, and eosinophilic granuloma. Some of these are rare diseases, such as lymphangioleiomyomatosis, which occurs in women of childbearing age, and acquired alveolar protein deposition due to granulocyte-macrophage colony-stimulating factor receptor deficiency. Experienced specialists are often able to make an accurate diagnosis and develop an appropriate treatment plan for their patients.