A Case of Optic Neuritis with Glial Fibrillary Acidic Protein Antibody and Secondary Ophthalmoplegia.

We report a case of optic neuritis and optic perineuritis complicated by secondary ophthalmoplegia in the setting of serum glial fibrillary acidic protein antibodies (GFAP-Abs) positivity. The patient, a 70-year-old woman, initially presented with right-sided visual loss, followed by ptosis and impaired ocular motility indicating involvement of cranial nerves III, IV, V1, and Ⅵ. Orbital MRI revealed a contrast-enhanced signal extending from the right optic nerve to the superior orbital fissure, accompanied by enhancement of the bilateral optic nerve sheath complex (ONSC). Optical coherence tomography demonstrated thinning of the peripapillary retinal nerve fiber layer in the superior quadrant of the right eye, accompanied by thinning of the ganglion cell-inner plexiform layer in both eyes. Humphrey visual field testing revealed central isopter constriction in the left eye. Visual evoked potentials revealed absence of the P100 wave in the right eye. Serum testing was positive for GFAP-Abs, while cerebrospinal fluid analysis was negative. Serum ANAs showed immunoreactivity to mouse optic nerve, whereas no serum GFAP antibody immunoreactivity was observed. The patient experienced clinical improvement following corticosteroid therapy; however, visual function did not recover. This case highlights a unique neuro-ophthalmologic presentation associated with serum GFAP-Abs positivity and potentially expands the clinical spectrum of GFAP astrocytopathy.