Herpes simplex virus infection of the placenta. The role of molecular pathology in the diagnosis of viral infection of placental-associated tissues.

Herpes simplex infections of the placenta and its associated tissues are rarely seen and, consequently, the pathologic features are not well understood. We describe the occurrence of herpes simplex virus infection of the placenta that was limited to maternal-derived cells of the subchorionic tissue. The microscopic findings were remarkable for both the absence of inflammation and characteristic viral inclusions. However, in situ DNA hybridization, as well as immunohistochemistry using antibody to herpes simplex virus type 2, revealed herpes virus infection of decidualized cells in the decidua capsularis. The significance of this finding, and the importance of molecular techniques for the diagnosis of herpes virus infection in placental pathology, are discussed.