Characterizing human herpes virus 6 following hematopoietic stem cell transplantation

Background: Human herpes virus 6 reactivation occurs in approximately 50% of patients following hematopoietic stem cell transplant, however, the significance of human herpes virus 6 reactivation remains uncertain. Methods: A retrospective study was conducted analyzing clinical data of patients testing positive for human herpes virus 6 by quantitative polymerase chain reaction following hematopoietic stem cell transplant from 1 January 1998 to 1 October 2011. Data retrieved were used to describe the clinical course and outcome of human herpes virus 6 positive hematopoietic stem cell transplant patients. Results: Sixty patients were identified who tested positive for human herpes virus 6 by polymerase chain reaction following hematopoietic stem cell transplant. A high proportion of patients were identified in this cohort with acute myeloid leukemia (28.3%), active disease (65%), transplanted with a matched unrelated donor (30%), ≥ 1 antigen mismatched (28.3%) matched unrelated donor, or an umbilical cord graft (25%), and those who received antithymocyte globulin (42.4%). Thirty-eight (63.3%) patients were treated for human herpes virus 6 with foscarnet alone or in combination with intravenous immunoglobulin, whereas 18 (30%) did not require treatment survival at Day 100 was 73.3%. Conclusion: This study suggests human herpes virus 6 reactivation occurs shortly after hematopoietic stem cell transplant (median of 25 days (interquartile range, 20-31.75) after hematopoietic stem cell transplant). Many potential risk factors are described in this report. Treatment of human herpes virus 6 predominately consisted of foscarnet with or without intravenous immunoglobulin; however, treatment of human herpes virus 6 was not always warranted. Furthermore, the effect of treatment on patient outcomes is uncertain.