A new study from Kyoto University has demonstrated that stem cell transplant patients who develop HHV-6 encephalitis have a significantly poorer prognosis than those who do not develop the condition. Only two of the eleven patients who suffered from post-transplant HHV-6 encephalitis in the study survived, both with persistent short-term memory loss. Symptoms including confusion, memory loss, and/or seizures occurred in all eleven patients, and HHV-6 encephalitis occurred in 8% of all transplants performed at the clinic. Of these eleven patients, two died of rapid exacerbation of HHV-6 encephalitis. In six of the patients, HHV-6 reactivation developed to encephalitis on the same day.
This finding further underscores the need to develop new treatment protocols to limit the development of HHV-6 encephalitis in stem cell transplant patients, as preemptive antiviral therapy administered immediately following the detection of HHV-6 reactivation did not prevent onset of HHV-6 encephalitis in any of the patients in this study. Given the severity of their findings, the authors suggest the early prophylactic use of antivirals such as foscarnet may be warranted to prevent this condition among all transplant patients. Furthermore, to echo a similar call from several recent publications, the group emphasizes that careful HHV-6 monitoring is particularly necessary among patients undergoing umbilical cord blood transplantation (CBT), who were found to be at a significantly higher risk of developing HHV-6 encephalitis than those receiving other sources of stem cell transplantation (p<.008).