Title : HHV6 encephalitis in an immunocompetent host
Abstract:
Introduction: A previously healthy and a fully vaccinated 5-year-old pre-schooler-aged male who presented to the ER with an insidious onset of decreasing level of consciousness and headaches before developing Status Epilepticus, and requiring admission to the PICU; with a final diagnosis of HHV6 Encephalitis based on the BioFire CSF testing.
HHV6 is known to cause CNS infections in immunocompromised individuals, particularly oncology patients; thus, its diagnosis in a previously healthy and an immunocompetent host sheds light on the suspicion, diagnosis, and treatment options for the aforementioned individuals.
Case Description: Presented was initially seen on the same day of the symptoms’ onset in a PHC, where he was prescribed Augmentin treating a throat infection.
Throughout the illness's course, he was becoming progressively more tired, confused, had developed decreasing eye-to-eye contact, and sleepiness.
He was later referred to our facility for further evaluation, when he started to have convulsions, and later on, Status Epilepticus.
Subsequently, he was transferred to the PICU, loaded with Phenytoin, and started on Midazolam IV.
A Brain MRI showed diffuse cortical/deep cortical changes along with DWI restriction and ADC changes, and was suggestive of Hypoxic-Ischemic changes
His initial CSF studies (analysis, culture, and viral panel were normal); however, based on his greatly worrying symptom progression, repeated CSF samples were taken, which came to be positive for HHV6.
He was started on Foscarnet and Ganciclovir; and started to show great improvement and return to his neurological baseline, with a repeated CSF study being negative for the virus.
Followed later on in the clinic, where he was on Keppra prophylaxis and on regular follow-up with Occupational Therapy and Speech-Language Pathology.
Discussion: Viral encephalitis is a medical emergency. It is an aseptic inflammatory process of the brain parenchyma associated with clinical evidence of brain dysfunction, significant morbidity, and mortality (Michael and Solomon 2012).
HHV6 is usually associated with Roseola, which manifests with high fever, URTI symptoms and the development of a rash after the fever subsides.
In immunocompromised patients (haematological malignancies and transplantation), reactivation of roseoloviruses may cause severe, lethal organ dysfunctions, including damage to the limbic system, brain stem, and hippocampus; thus, it could potentially lead to life-long disability.
Moreover, an HHV6 infection may lead to a chromosomally integrated human herpesvirus 6 status, in which the HHV-6 genome is integrated into the host’s genome and is vertically transmitted in a Mendelian manner; that itself may cast doubt on the recently utilized BioFire technology as it could lead to misdiagnose the causation of the illness, and the unnecessary initiation of antiviral therapy that requires strict monitoring and might lead to serious side effects.
The main purpose of presenting the case is to highlight the unique presentation of HHV6 Encephalitis in an immunocompetent host, and to discuss the challenges associated with suspecting the diagnosis, reliability of testing for the infection with a recently utilized technology, and the decision to proceed for, and types of management.
