Giant Cell Arteritis Presenting as Unilateral Arteritic Anterior Ischemic Optic Neuropathy.

Giant cell arteritis (GCA) is a rare inflammatory vasculitis of unknown cause that involves large and medium arteries. Arteritic anterior ischemic optic neuropathy (AAION) is attributed to vascular occlusion of the posterior ciliary arteries (PCAs) which supply the optic nerve head (ONH). AAION is the most common ophthalmic complication of GCA and can cause sudden and irreversible loss of vision with a high risk of involvement of the second eye. A 57-year-old female patient presented with unilateral sudden onset visual loss in the right eye (OD) for two days. It was accompanied by severe right-sided headache and scalp tenderness on the right temple, neck as well as the presence of jaw pain over the past three months. Visual acuity (VA) was hand motion (HM) OD, and 20/20 in the left eye (OS). Fundus examination revealed diffuse swollen optic disc with pallid "chalky white" appearance OD and normal healthy optic disc OS. A dramatically elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were found. Therefore, a diagnosis of GCA was made, and immediate IV methylprednisolone was started followed by oral prednisone doses. A right temporal artery (TA) biopsy was done later and was negative. On follow-up, VA has maintained at HM level OD, and no involvement of the second eye occurred. GCA is a rare form of vasculitis that can be difficult to diagnose especially in the setting of negative TA biopsy. We support the evidence that negative TA biopsy does not rule out clinically suspected GCA with elevated ESR and CRP and recommend keeping a low index of suspicion as immediate treatment is required to prevent irreversible vision loss.