Risk factors of human herpesvirus 6 encephalitis/myelitis after allogeneic hematopoietic stem cell transplantation

Background Human herpesvirus 6 (HHV-6) encephalitis/myelitis is now a well-known complication after allogeneic stem cell transplantation (allo-HSCT), particularly after cord blood transplantation (CBT). In this study, we evaluated the risk factors of HHV-6 encephalitis/myelitis. Methods We evaluated 253 patients who received allo-HSCT from 2007 to 2015 at our institute. HHV-6 encephalitis/myelitis was defined as HHV-6 DNA detection in the cerebrospinal fluid or peripheral blood by polymerase chain reaction in the presence of typical manifestations without other concurrent condition which led to the manifestations. Results HHV-6 encephalitis/myelitis occurred in 11 patients (4.5%, encephalitis; 3.7%, myelitis; 0.8%). Multivariate analysis showed CBT, mycophenolate mofetil (MMF) for graft-versus-host disease (GVHD) prophylaxis, history of allogeneic hematopoietic stem cell transplantation (allo-HSCT), and engraftment syndrome (ES) were significantly associated with incidence of HHV-6 encephalitis/myelitis (P=.025, P=.017, P=.017, and P=.014, respectively). Conclusion Although it has been shown that CBT, ES, and history of allo-HSCT are risk factors for HHV-6 encephalitis/myelitis, our study demonstrated MMF is also a risk factor for the disease. This article is protected by copyright. All rights reserved.