Severe Amnesia due to HHV-6 Encephalitis after Allogenic Stem Cell Transplantation

prednisolone (1 mg/kg b.d.). Concurrently, a noninfectious pneumonia was diagnosed, which was treated with the combination of prednisolone and diuretics. Prophylactically, he received fl uconazole, valacyclovir and co-trimoxazole. Patient and donor were both cytomegalovirus seronegative. Seven weeks after the transplantation the patient became confused. On neurological examination a profound loss of shortterm memory was noted; he was unable to retain any new information presented to him. There was also a retrograde amnesia for a few weeks and he was disorientated with regard to time and place. The neurological examination was otherwise normal including other cognitive functions such as attentiveness and concentration. Cyclosporin was discontinued and prophylactic vitamin B supplementation started. Because the possibility of a viral infection was considered, the dose of valacyclovir was raised to 3,000 mg/day. Laboratory investigation revealed no abnormalities except for a mild trombopenia and leucopenia. Vitamin levels were normal including thiamine, and the cyclosporin level was in the therapeutic range. An MRI of the brain the next day was unremarkable. Spinal fl uid analysis revealed normal protein and glucose levels, and a normal cell count. Polymerase chain reaction (PCR) on cerebrospinal fl uid samples was negative for herpes simplex virus types 1 and 2, Epstein-Barr virus, varicellazoster virus and cytomegalovirus but revealed the presence of HHV-6 DNA. IgG antibody against HHV-6 was detected while Dear Sir, Immunocompromised posttransplantation patients are susceptible to a variety of opportunistic infections and reactivation of latent viral infections. In the past years, human herpesvirus 6 (HHV-6) has been recognized as an important new viral pathogen in this group of patients. We report a 46year-old male who developed a severe shortterm memory dysfunction based on a HHV6 encephalitis after a bone marrow transplantation.