[Human herpes virus type 6, etiology of an acute encephalitis in childhood: case report].

Primary infection with human herpesvirus-6 (HHV-6) causes the classical roseola infantum. Otherwise the infection is clinically silent but it may sometimes be responsible for central nervous system involvement. In order to illustrate such a type of lesions, we report on a 16-month-old girl with acute leucoencephalitis. The disease started with pyrexia 40 degrees C, followed by an episode of seizure, erythematous rash on the trunk and then coma. Brain MRI showed wide lesions on white matter. HHV-6 DNA was detected by PCR in the CSF and serum at the acute stage, and tests for HHV-6 antibody showed a significant increase of IgG antibody titre between acute and convalescent sera. One month later complete clinical recovery was observed while the MRI showed a partial disappearance of the lesions. The sero-conversion associated with the detection of the viral DNA in the serum identified a primary HHV-6 infection and the detection of viral nucleic acid in CSF gives arguments for the responsibility of the virus in the pathogenesis. When facing an acute leuco-encephalitis in infants, it is important to perform exhaustive virology investigations to rule out the implication of HHV-6 as well as other commonly incriminated pathogens (EBV, CMV, mycoplasma, enterovirus) to avoid accusing wrongly the vaccines.