Pulmonary cryptococcosis is a subacute or chronic visceral fungal disease caused by new cryptococcal infection. This fungus belongs to the saprophytic yeast, does not form hyphae and spores, and is widely present in nature. Low immune function is the main cause of the disease. The fungus is mostly inhaled into the human body through the respiratory tract and forms infection foci in the lungs. It mainly invades the lungs and central nervous system, but can also invade bones, skin, mucous membranes and other organs. Healthy people can usually recover on their own after infection or the lesions are limited to the lungs, without clinical symptoms. When the resistance is reduced, it will cause the disease and can spread to the whole body through blood. The central nervous system is most likely to be affected, so cryptococcal meningitis and pneumonia are often suffered at the same time.