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Human Herpesvirus 6 Encephalitis in Immunocompetent and Immunocompromised Hosts
Giulia Berzero1, Giulia Campanini1, Elisa Vegezzi1
1From the Neuroncology Unit (G.B., E.V., E.M.), and Neuroradiology Unit (M.P., A.P.), IRCCS Mondino Foundation, Pavia; Molecular Virology Unit (G.C., F.B.), Microbiology and Virology Department, Diagnostic Radiology, Interventional Radiology and Neuroradiology Unit (A.M.S.), Bone Marrow Transplantation Unit (A.A.C., P.B., O.B.), Infectious and Tropical Diseases Unit (A.D.M.), Pediatric Clinic (V.R., T.F., S.S.), and Pediatric Hematology/Oncology (F.C., M.Z.), Fondazione IRCCS Policlinico San Matteo, Pavia; and Department of Brain and Behavioral Sciences (A.P.), Department of Molecular Medicine (P.B., O.B.), and Department of Clinical, Surgical, Diagnostic and Paediatric Sciences (F.B.), University of Pavia, Italy.
Objective:
The aim of this study was to analyze the clinical, radiologic, and biological features associated with human herpesvirus 6 (HHV-6) encephalitis in immunocompetent and immunocompromised hosts to establish which clinical settings should prompt HHV-6 testing.
Methods:
We performed a retrospective research in the virology database of Fondazione IRCCS Policlinico San Matteo (Pavia, Italy) for all patients who tested positive for HHV-6 DNA in the CSF and/or in blood from January 2008 to September 2018 and separately assessed the number of patients meeting the criteria for HHV-6 encephalitis in the group of immunocompetent and immunocompromised hosts.
Results:
Of the 926 patients tested for HHV-6 during the period of interest, 45 met the study criteria. Among immunocompetent hosts (n = 17), HHV-6 encephalitis was diagnosed to 4 infants or children presenting with seizures or mild encephalopathy during primary HHV-6 infection (CSF/blood replication ratio <<1 in all cases). Among immunocompromised hosts (n = 28), HHV-6 encephalitis was diagnosed to 7 adolescents/adults with hematologic conditions presenting with altered mental status (7/7), seizures (3/7), vigilance impairment (3/7), behavioral changes (2/7), hyponatremia (2/7), and anterograde amnesia (1/7). Initial brain MRI was altered only in 2 patients, but 6 of the 7 had a CSF/blood replication ratio >1.
Conclusions:
The detection of a CSF/blood replication ratio >1 represented a specific feature of immunocompromised patients with HHV-6 encephalitis and could be of special help to establish a diagnosis of HHV-6 encephalitis in hematopoietic stem cell transplant recipients lacking radiologic evidence of limbic involvement.
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