Background:In recent years, liver transplantation (LT) has become a well-accepted therapeutic modality for children with end-stage liver disease, with transplantation surgery being performed at a younger age. Human herpes virus 6 (HHV-6) infection occurs in most children within the first 2 years of life, therefore, data on primary HHV-6 infection in pediatric liver transplant recipients is scarce.Objective: To describe the course of primary HHV-6 infection after pediatric LT. Methods: Medical files, between the years 2015-2016, of post-LT pediatric patients with suspected primary HHV-6 infection were reviewed. Clinical and laboratory data for enrolled cases were evaluated. Primary infection was defined as DNAemia in children who were seronegative prior to transplantation or seroconversion from negative to positive IgG posttransplantation.Results: Four cases of primary HHV-6 (type B) infection were identified among the 26 children who had undergone LT at our center during the study period. All patients were <1 year old and presented with fever, hepatitis, and elevated inflammatory markers, most (75%) within a short-period posttransplantation. All were initially treated with empiric antibiotics for a suspected bacterial infection and three underwent liver biopsy, one showing signs of rejection. Three were treated with antiviral therapy with a gradual resolution of symptoms. Discussion:Primary HHV-6 should be taken into account in young children shortly after LT, especially when presenting with fever and elevated liver enzymes. Treatment with antiviral therapy should be considered. Conclusions:In young infants post-LT, a high index of suspicion may promote early detection of HHV-6 primary infection and prevent serious complications. K E Y W O R D Shuman herpes virus 6, infection, liver, pediatric, primary, transplantation | HHV-6 testing policyDuring the study period, laboratory tests were performed to detect HHV-6 when the patients displayed one or more of the following signs or symptoms: unexplained fever, rash, pneumonitis, splenomegaly, encephalitis, bone marrow suppression, hepatitis, or acute rejection as previously reported. 1,4 However, not all possible cases were tested.Testing for HHV-6 was performed in accordance with the attending physician's decision.