Human herpesvirus 6 can cause encephalitis early after allogeneic hematopoietic stem cell transplantation.

Human herpesvirus 6 (HHV-6) causes benign febrile illness or rash in >95% of children. It remains latent in the body thereafter but can become reactivated in severely immunocompromised individuals. Noting reports of HHV-6–associated neurologic disease in patients who had undergone allogeneic hematopoietic stem cell transplantation, investigators in Maryland undertook a retrospective investigation involving adults who underwent this procedure at the National Institutes of Health Clinical Center between 2009 and 2011.

The researchers identified 9 cases of HHV-6 encephalitis among 243 transplant recipients, with a median time of 21 days from transplant to symptom onset (range, 6 to 145 days). All patients presented with confusion and headache; only two had fever of unknown origin, but seven had prominent anterograde amnesia with variable concurrent disorientation and bradyphrenia. Magnetic resonance imaging revealed no abnormalities in any patients during the first week, but showed hyperintense lesions in the limbic region 7 to 10 days later in three patients and diffuse atrophy at 4 weeks in seven patients. Cerebrospinal fluid (CSF) analysis showed only minimal pleocytosis or protein elevation, but HHV-6 was detectable in the blood of eight patients and in the CSF of all nine. All patients received antiviral agents, with duration guided by clinical response and viral-load reduction. Five of the nine died, but only one had ongoing encephalitis at the time of death; two of the survivors had persistent memory deficits and anterograde amnesia for up to 2 years.

CITATION(S):

Bhanushali MJ et al. Human herpes 6 virus encephalitis complicating allogeneic hematopoietic stem cell transplantation. Neurology 2013 Mar 20; [e-pub ahead of print].