Pulmonary eryptococcosis is mostly caused by aspiration of Cryptococcus neoformans from the human environment. It occurs most often in immunosuppressed hosts, such as AIDS patients; about 20% occur in immunocompetent healthy individuals. Cryptococcus neoformans is a yeast that is widely found in nature. The yeast cells are 4-6?m in diameter and can be divided into four serotypes A, B, C and D according to the antigenicity of the podococcal polysaccharide. The route of infection is respiratory aspiration, newborn Cryptococcus with aerosol inhalation into the lungs can be cleared by neutrophils, natural killer cells and alveolar macrophages. If the amount of aspirated bacteria is large and exceeds the body’s defense function, the disease can develop. Pulmonary cryptococcosis forms granulomatous nodules or masses in the lung tissue, which may be single or multiple, about 1-8 cm in diameter, mostly under the pleura, and are often misdiagnosed as pulmonary tuberculosis or lung cancer. Microscopically, granulomas are seen to contain cryptococci and macrophages. Sometimes macrophages are arranged around the lesion in a way that resembles the structure of a tuberculosis nodule. Clinical symptoms may vary in severity and may be asymptomatic. In mild cases, there may be fever, dry cough, occasional small amounts of hemoptysis, malaise, and weight loss. In severe cases, there is shortness of breath and hypoxemia. The characteristic imaging sign is a subpleural nodule, which may also show pneumonia, multiple nodules, cavities, and mass-like damage. Histologic and microbiologic evidence is required for diagnosis. Microscopic detection of cryptococci on ink-stained smears of cerebrospinal fluid in cases of combined meningitis can help in the diagnosis. Treatment may include fluconazole, itraconazole, or amphotericin B.