A Rare Case Reveals Important Consideration of the Diagnosis of Giant Cell Arteritis in Patients with Bilateral Painful Optic Perineuritis.

Background and Clinical Significance: Giant cell arteritis (GCA) is an autoimmune vasculitis of both medium and large-sized vessels typically affecting females 50 years of age or older. Severe complications can include permanent visual loss, acute coronary syndrome, or stroke. This case will present an atypical presentation of bilateral OPN which can be a rare manifestation of GCA; Case Presentation: Our patient developed acute, painful worsening central vision loss progressing from right eye to left with bilateral extraocular motility restriction and magnetic resonance image (MRI) revealed bilateral, circumferential optic nerve sheath enhancement suggesting optic perineuritis (OPN). Temporal artery biopsy confirmed GCA with bilateral temporal arteritis. The patient was treated with a high dose course of corticosteroids followed by a taper and was started on upadacitinib with symptomatic improvement; Conclusions: This case underscores OPN as a rarer manifestation of giant cell arteritis that can present with bilateral painful eye movements and vision loss. Early recognition and prompt corticosteroid therapy are essential to prevent irreversible visual impairment.