[Human herpesvirus 6 encephalitis after bone marrow transplantation].

Human herpesvirus 6 (HHV-6) encephalitis may induce neurological sequelae and death; the diagnosis is difficult because of an initially poor symptomatology and of the absence of specific biochemical, electric and radiological signs. We report on a 7-year-old boy with relapsed acute lymphoblastic leukaemia, who developed HHV-6 encephalitis after bone marrow transplantation; the patient recovered after treatment with ganciclovir.