A group from Fujita Health University has identified the first known case of posterior reversible encephalopathy syndrome (PRES) associated with HHV-6B encephalitis in a child following hematopoietic stem cell transplantation (HSCT). PRES is a syndrome characterized by headaches, confusion, seizures and visual disturbances associated with transient, predominantly posterior white matter changes on neuroimaging studies. In this case, an 11-year old child who underwent HSCT was diagnosed with PRES based on clinical and neuroimaging findings, and high levels of HHV-6B DNA were detected in both serum and CSF. While full resolution of neurological symptoms was observed in response to ganciclovir treatment, the patient died on day 105 post-transplant due to GVHD.
Recent evidence from the same group suggests that the pathogenesis and clinical features of HHV-6B encephalitis differ in patients with primary infection compared to those with HHV-6 reactivation (Kawamura 2011). The group also reported HHV-6B reactivation preceding the onset of neurological symptoms. This was followed by up-regulation of inflammatory cytokines and IL-8, which the group suggests may be indicative of a trigger for onset of PRES in the CNS. This finding, taken together with other evidence presented in the case report, suggests that the use of antiviral drugs which inhibit HHV-6B reactivation in the CNS may be more useful than anti-cytokine treatments for the treatment of PRES. The group is initiating similar analyses on a larger number of cases to further elucidate the precise pathophysiology and the optimal treatment strategy for HHV-6B-associated PRES.