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

Abstract 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.