Human Herpesvirus 6 Encephalitis in Immunocompetent and Immunocompromised Hosts

Abstract

ObjectiveThe 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.MethodsWe 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.ResultsOf 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.ConclusionsThe 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.

A Rare Case of HHV-6 Encephalitis in an Immunocompetent Host: Case Report and Literature Review

“…These complications include encephalitis, acute necrotizing encephalitis, acute encephalopathy with biphasic seizure syndrome, and/or demyelinating disease [ 3 ]. HHV-6 encephalitis can occur in an adult as a primary infection or reactivation, but often it occurs in the immunocompromised, hematopoietic stem cell transplantation (HSCT) patients, and solid organ transplant recipients [ 4 - 5 ]. Our 26-year-old adult patient fell outside of these three categories as he was immunocompetent without a history of HSCT or organ transplantation.…”

Incidental Detection of Human Herpesvirus-6 in Cerebrospinal Fluid Analysis: To Treat or Not to Treat?

“…Human herpesvirus-6 (HHV-6) is a DNA virus that demonstrates near-universal infection in childhood, affecting more than 80% of children by two years of age [1][2][3][4][5][6][7][8][9][10]. With a varied range of infections, HHV-6 has been shown to induce an asymptomatic disease state in a majority of those affected, and infrequently cause febrile seizures, encephalitis, or meningitis in some [1].…”

“…HHV-6 establishes a latent state in monocytes and macrophages and can reactivate in vulnerable populations such as the immunocompromised [1,6,10]. In those affected with neurological disease, HHV-6 may result in long-term neurological sequela and significant morbidity [10].…”

Long-term outcome in corneal endotheliitis with molecular detection of herpes simplex virus 1 and human herpes virus 6: a case report

“…The clinical significance of HHV-6A infection has not been well demonstrated, although HHV-6B has been shown to be the major agent causing exanthema subitem (roseola infantum) as a primary infection [ 5 ], with > 90% of the general population developing a latent condition [ 6 ]. Reactivation of HHV-6B has been demonstrated to be related to encephalitis [ 7 ] and hypersensitivity syndrome in immunocompetent hosts [ 8 , 9 ]. Furthermore, HHV-6B has been detected in various ocular diseases, including keratitis, uveitis, optic neuritis, and endophthalmitis; Sugita et al performed multiplex polymerase chain reaction (PCR) analysis in 350 samples of uveitis or endophthalmitis and in 65 samples of corneal inflammatory diseases, and demonstrated that 2 and 1.5% of them were positive for HHV-6 DNA, respectively [ 10 ].…”