Patients with cytomegalovirus pneumonia commonly have glassy, corn-like or nodular changes in both lungs on chest radiographs and CT. Cytomegalovirus (CMV) is a viral pneumonia characterized by the formation of large type A eosinophilic intranuclear and intracytoplasmic inclusions in infected cells. Most are asymptomatic occult infections, but in immunocompromised and infants can cause severe lung infections leading to death. In recent years with the introduction of bone marrow and organ transplantation and the increasing number of AIDS patients, CMV has become the most common causative agent in both cases. I. Pathogenesis Cytomegalovirus belongs to group B herpesvirus, which is a double-stranded DNA virus with an outer envelope and a spherical nucleus. CMV has two antigens, complement binding antigen and neutralizing antigen. The former exists mostly in the form of soluble antigens, while the latter is mainly composed of glycoproteins and is one of the components of the viral envelope.CMV infection is strictly species-specific, and humans are only infected by human cytomegalovirus, which grows and multiplies slowly in cells (2-3 months to show obvious lesions). Infected cells have enlarged nuclei and increased cytoplasm, forming typical eosinophilic intranuclear and intracytoplasmic inclusion bodies. CMV can be transmitted by various routes, mainly by contact transmission in infants and children, and mainly by sexual contact in adults. CMV infects a variety of immunologically active cells, including epithelial and mesenteric vascular endothelial cells, T cells, B cells, and NK cells, and replicates in the body after infection, increasing the size of the infected cells with focal necrosis in the center and releasing newly synthesized virus to further infect surrounding cells. The infected cells increase in size, have focal necrosis in the center, and release newly synthesized viruses that further infect surrounding cells. The infected cells in the lung tissue are mainly alveolar cells and macrophages, which after infection develop diffuse interstitial lung edema, fibrosis and alveolar swelling, focal necrosis, hemorrhage and hyperplasia, resulting in hypoxemia. Because cellular immunity plays a major role in the fight against CMV infection, the condition is particularly severe in patients with cellular immunodeficiency (e.g., post-bone marrow transplantation and AIDS patients) who develop CMV infection.