Human herpesvirus‐6B infection in pediatric allogenic hematopoietic stem cell transplant patients: Risk factors and encephalitis

Background Human herpesvirus‐6B (HHV‐6B) infection after allogenic hematopoietic stem cell transplantation (allo‐HSCT) is known to be associated with post‐transplant limbic encephalitis in adults. Meanwhile, the association between HHV‐6B infection and central nervous system complications remains unclear in pediatric allo‐HSCT patients. Methods In this study, HHV‐6B infection was monitored for more than 50 days after HSCT using virus isolation and real‐time PCR. Clinical information such as patient background and encephalitis status was collected retrospectively from medical records. Risk factors for HHV‐6B infection were determined by the Cox proportional hazards model, and the clinical features of HHV‐6B encephalitis in pediatric allo‐HSCT patients were elucidated. Results Human herpesvirus‐6B infection was observed in 74 (33.8%) of 219 patients at 3‐47 days (median 18, interquartile range 13‐20). Risk factors identified in multivariable analysis were hematological malignancy (hazards ratio [HR], 5.0; 95% confidence interval [CI], 2.3/12.5; P