Chromosomally integrated human herpesvirus‐6 in transplant recipients

Human herpesvirus‐6 (HHV‐6) is unique among human herpesviruses because of its ability to integrate into chromosomes. This entity, termed chromosomally integrated HHV‐6 (CIHHV‐6), is often mistaken for active infection and treated unnecessarily. The clinical significance of CIHHV‐6 in transplant recipients is not defined. Herein, the clinical characteristics of 7 liver transplant patients with CIHHV‐6 from our recent study, together with 14 other published cases of CIHHV‐6 were reviewed. Of the 21 cases, CIHHV‐6B was reported most commonly among solid organ transplant recipients, while CIHHV‐6A was mostly seen in allogeneic hematopoietic stem cell recipients. None of the 21 patients developed clinical symptoms related to HHV‐6 after transplantation. However, antiviral therapy was administered to 5 asymptomatic patients mistaken to have HHV‐6 infection because of their very high HHV‐6 DNA levels, 3 who developed symptomatic cytomegalovirus disease, and 1 with graft‐versus‐host disease that was mistaken for HHV‐6 infection. In patients who received antiviral therapy, there was no apparent decline in HHV‐6 DNA load, although change in viral kinetics is difficult to discern in the setting of high baseline HHV‐6 DNA load. Clinicians should be aware of this entity of CIHHV‐6 so that antiviral therapy can be considered in the proper clinical context.