Epstein-Barr Virus Encephalitis Presenting As Acute Disseminated Encephalomyelitis: A Challenging Diagnostic Dilemma.

Epstein-Barr virus (EBV) is a common human herpesvirus associated with a wide range of clinical manifestations, primarily affecting the lymphoid system. However, central nervous system (CNS) involvement, although rare, can occur and present a diagnostic challenge, particularly in immunocompetent individuals. We present a case of a 28-year-old healthy female who initially presented with a flu-like illness, her symptoms rapidly progressed, leading to neurological deficits, and altered mental status. The patient's diagnostic workup, including a viral panel and various antibodies, failed to provide a conclusive diagnosis. However, lumbar puncture revealed significant abnormalities in cerebrospinal fluid (CSF), including elevated white blood cell count and elevated CSF protein. Neuroimaging studies demonstrated non-specific findings in subcortical white matter, pontomedullary junction, and extended spinal cord lesion. Tragically, the patient's condition rapidly worsened, with diffuse cerebral edema observed on repeat imaging, leading to the patient's demise even after conventional treatment. CSF analysis, performed at an apex lab, unexpectedly returned positive for EBV PCR, indicating a diagnosis of EBV encephalitis or EBV-associated acute disseminated encephalomyelitis (ADEM). This case highlights the challenges encountered in diagnosing EBV-associated CNS manifestations, especially in immunocompetent individuals, where these presentations are exceedingly rare. The atypical clinical course, negative initial laboratory investigations, and absence of specific radiological findings further complicated the diagnostic process. Early recognition and consideration of infectious etiologies, including EBV, in patients presenting with unexplained encephalitis or ADEM-like symptoms, are essential for timely intervention and optimal patient outcomes.