2012 Volume 1 Issue 3 Pages 76-92
Human herpesvirus (HHV)-6 reactivation is common (30-50%) after allogeneic hematopoietic cell transplantation (allo-HCT), and is linked to various clinical manifestations. HHV-6 has been recognized as an important pathogen that can cause encephalitis after allo-HCT. HHV-6 encephalitis typically develops around 2-6 weeks after allo-HCT, and is characterized by short-term memory loss, loss of consciousness, and seizures. Magnetic resonance imaging typically shows bilateral signal abnormalities in the limbic system. Umbilical cord blood transplantation is associated with increased risk of HHV-6 encephalitis. While antiviral therapy using ganciclovir or foscarnet is recommended as a first-line therapy for HHV-6 encephalitis, mortality rates attributable to this pathology remain high. Even among survivors, many patients display cognitive sequelae. Establishment of optimal strategies is urgently needed to prevent HHV-6 encephalitis. Besides encephalitis, associations between HHV-6 and various important post-transplant complications have been reported, including pneumonitis, gastroenterocolitis, hepatitis, bone marrow suppression/graft failure, graft-versus-host disease, and cytomegalovirus infection. Further investigations are needed to determine the roles of HHV-6 in these manifestations.
