Atypical Presentation of Clinically Isolated Syndrome and Optic Neuritis in a Patient with Active HepatitisC Infection

Optic neuritis is associated with demyelinating diseases such as multiple sclerosis (MS), but atypical presentations, particularly bilateral optic nerve involvement or coexisting sys-temic symptoms, warrant broader diagnostic consideration. This case report describes a 50-year-old male with untreated, active Hepatitis C virus (HCV) infection who presented with bilateral optic neuritis. Cerebrospinal fluid analysis revealed elevated myelin basic protein, oligoclonal bands, and a high IgG index and an elevated Hepatitis C viral load of 9.3 million IU/mL. MRI orbit showed bilateral optic neuritis/perineuritis. The patient had no history of interferon therapy and lacked markers of cryoglobulinemia, making this a ra-re case of optic neuritis likely related to chronic HCV infection. Treatment was complicated by concerns of exacerbating infection, leading to administration of IVIG without cortico-steroids. This case contributes to the expanding spectrum of multiple sclerosis (MS) mimics and highlights the diagnostic challenges in atypical optic neuritis presentations, especially in the setting of systemic viral infections.