Limbic encephalitis is a rare neurological syndrome, which develops after stem cell transplantation, and is characterized by a series of neurological symptoms, including retrograde amnesia, behavioral disturbance, and progressive intellectual deterioration and high signal intensity in the hippocampus on magnetic resonance imaging (MRI). Herein is described the case of a patient with limbic encephalitis, which developed after allogeneic bone marrow transplantation, and was possibly due to HHV-6 infection. An 18-year-old man, with acute lymphoid leukemia, who underwent HLA-matched unrelated donor bone marrow transplantation, developed a fever and chill accompanied by neurological symptoms, including behavioral disturbance and retrograde amnesia, during the bone marrow recovery phase. A brain MRI revealed bright signal-intensity in both hippocampi. Examination of his cerebrospinal fluid suggested viral encephalitis. Based on these findings, a diagnosis of viral limbic encephalitis was highly suspected. Tests for casual causes of viral limbic encephalitis, including the CMV, HZV and HSV-1 and 2, in serum or CSF were all negative. The encephalitis responded well to ganciclovir therapy.

Keywords: Limbic encephalitis, Allogeneic stem cell transplantation, HHV-6