DIAGNOSIS OF HUMAN HERPESVIRUS-6 INFECTION IN 2 PATIENTS WITH CENTRAL-NERVOUS-SYSTEM COMPLICATIONS

Background: Although exanthem subitum (ES) is generally a mild, self-l imiting disease of early childhood, some cases of ES are complicated b y seizures and encephalopathy. The presence of human herpesvirus-6 (HH V-6) DNA in cerebrospinal fluid (CSF) of these patients suggests that HHV-6 can infect the central nervous system (CNS) causing encephalitis . Objectives: To demonstrate HHV-6 infection in two patients with seri ous CNS complications. The patients, a child and an adult, failed to d evelop the characteristic rash normally associated with ES. Study desi gn: Peripheral blood mononuclear cells (PBMCs) and CSF were examined f or the presence of HHV-6 or viral DNA, using virus isolation technique s and the polymerase chain reaction (PCR). Serum samples were tested b y immunofluorescence (IF) and enzyme linked immuno-sorbent assay (ELIS A) for the presence of anti-HHV-6 IgM and anti-HHV-6 IgG respectively. Results: HHV-6 was isolated from the PBMCs of the adult patient and t he presence of virus in these cells was confirmed using electron micro scopy. HHV-6 DNA was detected in CSF taken early during the infection in both patients, together with anti-HHV-6 IgM antibodies and increasi ng levels of anti-HHV-6 IgG. Conclusions: The diagnosis of HHV-6 infec tion in these patients was confirmed either by virus isolation or by t he detection of HHV-6 DNA in the CSF, and the results of serology. The se cases show that HHV-6 infection may result in serious CNS complicat ions, in children and adults.