Pneumocystis carinii pneumonia, or Pneumocystis carinii pneumonia, is an interstitial pneumonia caused by infection with Pneumocystis carinii. It is the most common opportunistic infection in AIDS and accounts for about half of all deaths due to opportunistic infections. It is also seen in malnourished infants and children or in immunosuppressed individuals. The characteristic lesion of the disease is a large amount of foamy, eosinophilic exudate filling the alveolar lumen, the latter consisting of a large amount of immunoglobulin and mycobacteria, with a large infiltrate of macrophages, lymphocytes, and plasma cells seen in the alveolar septa and alveolar lumen, and granulomatous lesions in some areas. Silver staining may show foamy exudates or walls of Pneumocystis carinii in macrophage plasma. The diagnosis can be confirmed in about 50% of patients by pathogen examination of lung lavage fluid. Clinically, patients mainly present with fever, cough, dyspnea, and hypoxia, and their lesions may recover with early diagnosis and timely treatment. Pneumocystis carinii pneumonia treatment should first eliminate inflammation, control infection, available antibiotics for bactericidal treatment, preferred compound sulfamethoxazole tablets for treatment. If the patient suffers from Pneumocystis carinii pneumonia, it is recommended to actively go to the hospital, under the doctor’s instructions to use medication, do not take medication on your own, so as not to delay the condition.