Risk Factors and Outcome of HHV-6 Infections After Allogeneic Hematopoietic Cell Transplantation.

BACKGROUND

Human herpesvirus 6 (HHV-6) reactivation is frequently seen in recipients of allogeneic hematopoietic cell (HCT) transplantation, but data on clinical outcomes and risk factors are scarce. We aimed to assess the epidemiological features and outcome of clinically relevant HHV-6 infections in the first 180 days after transplantation.

METHODS

This was a single-center retrospective study of 405 consecutive allogeneic HCT recipients. We matched cases with a clinically relevant HHV-6 infection with control patients.

RESULTS

We found an cumulative incidence of 3.7% (95% confidence interval [CI], 1.9-5.5) and an overall incidence rate of 8.84 per 100 person-years (95% CI, 4.95-14.6) of clinically relevant HHV-6 infections during the study period. Adjusting for HCT-specific comorbidity index category, conditioning regimen, donor type, and acute graft-versus-host disease severity, the occurrence of HHV-6 encephalitis was significantly associated with a higher hazard of nonrelapse mortality (hazard ratio, 3.821; 95% CI, 1.437-10.155; = .007). We observed a significantly higher mortality risk for cases compared to controls ( = .04) and found female sex ( = .017) and use of steroids ( = .023) or sirolimus ( = .006) as risk factors for HHV-6 infection. All cases had lymphopenia (<500/µL) at the day of diagnosis and 80% developed acute graft-versus-host disease around the HHV-6 infection.

CONCLUSIONS

HHV-6 encephalitis remains the most detrimental disease manifestation and posttransplant factors related to immune suppression are to be included in future epidemiological studies.