Little is known about human herpesvirus-6 (HHV-6) in leukemia patients. We prospectively followed 37 leukemia patients at risk for mold infection. HHV-6 DNA was detected from whole blood specimens in 11 patients (30%). History of granulocyte transfusions (p=0.05) and prior relapse of leukemia (p=0.07) were the only independent predictors of HHV-6 DNAemia. Haematologica. 2008 Jan; 93:(1) 157-158. DOI: 10.3324/haematol.11638 Little is known about Human Herpesvirus-6 (HHV-6) infection in patients with leukemia.1 We aimed to determine the frequency, risk factors, clinical characteristics, and outcome of HHV-6 DNAemia in adult patients with leukemia. We prospectively followed a cohort of leukemia patients seen at our institution (October 2002-March 2004 enrolled in a study assessing molecular diagnostic methods for Aspergillus, Cytomegalovirus (CMV), and HHV-6. Consecutive patients were enrolled if they were at risk for, or had a possible, probable, or proven invasive mold infection according to the European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria.2 Our institutional review board approved the study.Whole blood specimens were examined for HHV-6 using real-time PCR. Sequences for HHV-6 duallabeled probe and primers used in the study were as follows:Characteristics of patients with and without HHV-6 DNAemia were compared. The variables on univariate analysis with a p value <0.1 were entered into a multivariate unconditional logistic regression model. All statistical tests were 2-sided, and p ≤0.05 were considered significant. The statistical analyses were performed using Epi Info (version 3.2.2.) software (Centers for Disease Control and Prevention, Atlanta, GA, USA) and SAS 9.1 statistical software (SAS Institute Inc., Cary, NC, USA).Thirty-seven patients with leukemia were enrolled, with HHV-6 DNAemia detected in 11 of them (30%) (Online Supplementary Table 1). Four of the 11 patients (36%) had received transfusions of irradiated granulocytes prior to the onset of HHV-6 DNAemia from donors whose granulocyte counts had been stimulated with hematopoietic growth factors and who had not been screened for HHV-6. The median number of granulocyte transfusions was 11 (range 3-16), with a median time from first granulocyte transfusion to onset of HHV-6 DNAemia of 44 days (range 2-117 days). HHV-6 infection was not suspected in any patient. Presentations at the first positive result for HHV-6 were mainly unexplained fever and lower respiratory infection (Online Supplementary Table 2). Compared to the 26 patients without HHV-6 DNAemia, those with HHV-6 DNAemia were more likely to have diarrhea, and apparently a higher incidence of rash. Neurological symptoms were comparable between the two groups (Online Supplementary Table 2).By univariate analysis, HHV-6 DNAemia was significantly associated with a history of granulocyte transfusions, diarrhea and viral coinfections (CMV and respiratory viruses in 2 patients each), with a trend towards prior relapse of leukemia. By multivariate analysis...