Inherited chromosomally integrated human herpesvirus-6 in a patient with XIAP deficiency.

Human herpesvirus-6 (HHV-6) is a common pathogen affecting the human population. Primary HHV-6 infection generally occurs during infancy and causes exanthema subitum. Moreover, HHV-6 may exhibit inherited chromosomally integrated HHV-6 (iciHHV-6) in certain individuals. Although iciHHV-6 is generally known to be nonpathogenic, it may cause reactivation in patients with primary immunodeficiency disease (PID). XIAP deficiency is a rare PID characterized by recurrent hemophagocytic lymphohistiocytosis (HLH). It has been reported that the Epstein-Barr virus primarily causes HLH; however, the other pathogens, including HHV-6, can also cause this complication. We encountered a case of XIAP deficiency accompanied by iciHHV-6. He suffered from recurrent HLH, for which allogeneic bone marrow transplantation (BMT) was performed as a curative therapy. During the course of BMT, the patient experienced HLH three times, but there was no reactivation of endogenous HHV-6 from iciHHV-6. Finally, the patient achieved complete donor chimerism and a decline in HHV-6 DNA copy number in whole blood. This case report demonstrates no evidence of reactivation of iciHHV-6 during BMT in a patient with XIAP deficiency.