Complete Recovery From Human Herpesvirus 6 (HHV-6) Encephalomyelitis in an Immunocompetent Adult: A Rare Cause of Paraparesis and Ataxia.

Human herpesvirus 6 (HHV-6) is a commonly acquired virus in early childhood, typically resulting in a benign and self-limited illness. However, its neuroinvasive potential in adults, particularly in immunocompetent individuals, remains underrecognized and diagnostically challenging. Clinical features such as nonspecific fever, respiratory symptoms, and evolving neurological deficits can mimic autoimmune demyelination, post-infectious encephalitis, or other viral myelitides, potentially delaying recognition and treatment. We report the case of a previously healthy 32-year-old male who presented with fever, lower respiratory symptoms, and progressive neurological deficits, including lower limb weakness, gait instability, and sensory abnormalities suggestive of spinal cord involvement. Initial imaging was inconclusive, but cerebrospinal fluid analysis revealed lymphocytic pleocytosis, elevated protein, and was positive for HHV-6 by Polymerase Chain Reaction (PCR). The patient was treated with intravenous ganciclovir and immunoglobulin, leading to clinical improvement and viral clearance. This case highlights the importance of considering HHV-6 in the differential diagnosis of acute encephalomyelitis, even in immunocompetent adults, and demonstrates that early antiviral and immunomodulatory therapy can lead to favorable neurological outcomes.