Severe optic neuropathy as initial manifestation of pachymeningitis hypertrophy from granulomatosis with polyangiitis.

Granulomatosis with polyangiitis (GPA) is a systemic necrotizing vasculitis that may involve the central nervous system, most frequently as hypertrophic pachymeningitis. We report the case of a 49-year-old woman who presented with bilateral, painless visual loss as the initial manifestation of GPA. Imaging revealed hypertrophic pachymeningitis with bilateral optic canal involvement. Despite extensive investigation, the diagnosis was only confirmed 3 years later through lacrimal gland biopsy, which demonstrated granulomatous inflammation with necrosis and vasculitis. The patient was treated with cyclophosphamide and later azathioprine, achieving clinical stability, though without recovery of vision. This case highlights that optic neuropathy due to pachymeningitis may precede classic systemic features of GPA, reinforcing the importance of early suspicion to prevent irreversible complications.