Human Herpesvirus 6 Associated With a Secondary Central Nervous System Vasculitis in an Immunocompetent Adult: A Case Report.

Human herpesvirus 6 (HHV-6) encephalitis typically affects children under three years of age, and adult cases are rare, usually occurring in immunocompromised individuals such as hematopoietic stem cell transplant recipients. HHV-6 can establish latency and reactivate under conditions of immunosuppression. Several neurotropic viruses, including varicella-zoster virus and herpes simplex virus, are known to induce central nervous system (CNS) vasculitis, but HHV-6 has not been clearly associated with this complication. We report the case of a 46-year-old immunocompetent woman presenting with encephalopathy, hemiparesis, and cerebellar signs. Brain MRI revealed ischemic lesions in multiple vascular territories and imaging features suggestive of cerebral vasculitis. Cerebrospinal fluid polymerase chain reaction (CSF PCR) was positive for HHV-6. Other etiologies, including neoplastic and autoimmune causes, were ruled out. The patient was treated with ganciclovir and dexamethasone at doses appropriate for CNS vasculitis. This case highlights a rare presentation of HHV-6-associated CNS vasculitis in an immunocompetent host and emphasizes the need to consider viral etiologies in the differential diagnosis of CNS vasculopathies.