Early human herpesvirus type 6 reactivation after allogeneic stem cell transplantation: a large-scale clinical study.

This study investigated the impact of human herpesvirus type 6 (HHV6) reactivation within 100 days of allogeneic stem cell transplantation (allo-SCT) on patient outcomes. HHV6 plasma loads were monitored weekly by quantitative PCR. Of 235 consecutive patients, 112 (48%) had an early positive HHV6 PCR test (group A) and 123 (52%) did not (group B). HHV6 reactivation was less frequent in patients who received reduced-intensity conditioning (P = .028). In group A, only 6 patients (5%) were asymptomatic; the most common clinical manifestations were fever (n = 60), skin rash (n = 57), diarrhea (n = 51), pulmonary complications (n = 19), and neurologic disorders (n = 12). Compared with the patients in group B, those in group A experienced delayed platelet engraftment (P = .003) and more frequent grade II-IV acute graft-versus-host disease (GVHD) (47% versus 30% in group B; P = .009). In multivariate analysis, the most important factors influencing the development of grade II-IV acute GVHD development were early HHV6 reactivation (P = .03) and unrelated donor status (P < .001). HHV6 reactivation adversely influenced 6-month survival (P = .04). Of the 38 evaluable patients receiving antiviral treatment, 34 had a significantly decreased HHV6 load. Our findings indicate that HHV6 reactivation after allo-SCT is associated with delayed platelet engraftment, early posttransplantation mortality, and the development of acute GVHD. Careful monitoring of HHV6 by PCR is warranted during the early posttransplantation period. Biol Blood Marrow Transplant 18: 1080-1089 (2012) (C) 2012 American Society for Blood and Marrow Transplantation