Abstract • 169

Parvovirus B19, has potent erythroid cell tropism, replicating only in red blood cell progenitors, and using globoside (blood group P antigen) as its receptor. B19 is the only known human pathogenic parvovirus: different disease manifestations depend on the immunological and hematological status of the host. In normal immunocompetent individuals B19 is the cause of an innocuous rash illness, erythema infectiosum, but in persons with underlying hemolytic disorders, B19 produces transient aplastic crisis, and in immunosuppressed patients, persistent B19 viremia manifests as pure red cell aplasia and chronic anemia. The outcome of fetal infection is critically dependent on the stage of pregnancy, and although systematic studies have shown evidence for congenital abnormalities following B19 infection, infection in the mid-trimester when the immune response is still immature - and the red cell mass is rapidly expanding - may lead to fetal death in utero, hydrops fetalis or the development of congenital anemia. The role of fetal B19 infection in constitutional bone marrow failure such as Diamond-Blackfan anemia is still under investigation. During early pregnancy, globoside is expressed on other tissues, including cardiac myocytes, and B19 induced-myocarditis may contribute to fetal pathology.