Optic Neuritis as an Initial Presentation of Granulomatosis with Polyangiitis: Two Case Reports

Introduction - Granulomatosis with polyangiitis (GPA) is a rare systemic vasculitis predominantly involving the respiratory tract and kidneys. While ocular manifestations occur in approximately 50% of cases, optic neuritis at disease onset is rare. We describe two cases where optic neuritis was the initial presentation of GPA.Case Report - Case 1 - A 51-year-old previously healthy man presented with headache, visual loss in the left eye (LE). Examination revealed a visual acuity (VA) of 20/20 in the right eye (RE) and counting fingers in the LE.  A relative afferent pupillary defect was observed in the LE. Brain and orbit MRI showed pachymeningitis, an expansive lesion in left orbital apex, and an enhanced lesion in the left optic nerve. Biopsy findings were consistent with GPA. Despite treatment with corticosteroids and cyclophosphamide, he developed loss of vision in the RE. VA declined to counting fingers in the RE and no light perception in the LE.Case 2 - A 56-year-old man developed painful visual loss in the RE. The diagnosis  of optic neuritis was made and he received IV pulses of methylprednisolone, resulting in RE amaurosis. Four months later, he developed painful LE amaurosis with no response to IV methylprednisolone. He was then referred to our Center. Examination revealed bilateral amaurosis, ophthalmoplegia in both eyes, and necrotizing scleritis, leading to perforation of the RE. MRI demonstrated bilateral optic nerve enhancement and hyperintense lesions in the apex of both orbits. Biopsy confirmed GPA. No improvement was observed following tretment with cyclophosphamide and steroids.. Treatment was subsequently changed to rituximab.Conclusion: These cases highlight that optic neuritis may occur at the onset of GPA, contributing to its severe outcomes. Early identification of the nature of the optic neuritis and appropriate treatment are essential to avoid catastrophic outcomes.