ABSTRACTA case of recurrent cytomegalovirus reactivations in a cytomegalovirus-seropositive woman who received allogeneic cord blood transplantation is described. Thirteen months posttransplantation, her CD3+T cell count was extremely low whereas natural killer cells represented 66% of her total lymphocytes. She showed defective thymic function that might contribute to the onset of valganciclovir resistance.