- Abstract A patient with the acquired immunodeficiency syndrome (AIDS) with a cytomegalovirus (CMV) infection localized in the area of an ileal Kaposi sarcoma resulting in perforation is described. Because only one case of such an association of Kaposi sarcoma with CMV leading to perforation has been reported, the presence and distribution of CMV-related nucleic acids and proteins in the affected segment of intestine were evaluated. By using in situ hybridization and immunocytochemical analyses the presence of CMV was shown within epithelial, endothelial, smooth muscle, and inflammatory cells at the site of perforation. This study not only confirmed that CMV can be detected in virtually all components of the intestinal wall despite the absence of distinctive cytomegalic changes, but also generated critical information that illustrates the usefulness of immunohistochemistry and in situ hybridization in elucidating the pathogenesis of CMV-associated lesions. These findings lend further support to the concept that CMV plays a pivotal role in the pathogenesis of intestinal perforation and emphasize the critical importance of in situ hybridization in gaining insight into the mechanisms of CMV-induced injury.