Unsuspected varicella-zoster virus encephalitis in a child with acquired immunodeficiency syndrome

We report a case of progressive encephalitis caused by varicella-zoster virus (VZV) in an adolescent with hemophilia and acquired immunodeficiency syndrome but without cutaneous signs of VZV infection. Magnetic resonance imaging of the brain demonstrated an abnormally increased periventricular signal in T2-weighted images. Infection with VZV was proved by in situ hybridization and immunofluorescence staining of brain tissue, which showed histologic evidence of herpesvirus infection. Encephalitis caused by infection with VZV is a potentially treatable complication of acquired immunodeficiency syndrome and requires a high index of suspicion for diagnosis.