Human herpesvirus-6 encephalitis during hematopoietic stem cell transplantation leads to poor prognosis

Introduction Indications for the application of hematopoietic stem cell transplantation (HSCT) from alternative donors have remarkably broadened in scope; however, the incidence of infections that lead to failure of HSCT, such as human herpesvirus-6 (HHV-6) encephalitis, has also increased. Methods We analyzed risk factors for symptomatic HHV-6 reactivation and the development of HHV-6 encephalitis in 140 consecutive adult patients who received allogeneic HSCT at our institution. Stem cell sources for the recipients were as follows: related-donor bone marrow in 40, related-donor peripheral blood in 5, unrelated bone marrow in 67, and unrelated cord blood in 28. Results Symptomatic HHV-6 reactivation occurred in 22 patients (16%), and 11 patients manifested encephalitis. Multivariate Cox proportional hazards regression analysis identified cord blood cell transplantation (CBT) as an independent predictor of HHV-6 reactivation (P=0.008). Hyponatremia or hypernatremia at the time of HHV-6 reactivation was detected before the development of HHV-6 encephalitis in 2 or 4 patients, respectively. Two patients died of HHV-6 encephalitis and 6 patients died of relapse of underlying diseases. Survival analysis identified higher risk of the disease (P=0.021) and HHV-6 encephalitis (P=0.003) as independent risk factors for reduced overall survival. Conclusion In cases involving CBT or unrelated-donor transplantation, patients should be carefully monitored for the symptomatic reactivation of HHV-6.