History
Mr. Ng was a 70-year-old man with a history of ANCA-associated vasculitis of renal, pulmonary, and ENT manifestations 5 years ago. He remained in remission on azathioprine 50mg daily. He did not have any other vascular risk factors.
He presented with a 3-week history of acute onset painless, altitudinal, monocular visual loss that occurred in rapid succession to involve both eyes.
Physical examination
On physical examination, his neurologic examination was pertinent for asymmetrical visual field defects in both eyes. The superior quadrants were affected in the right eye and the inferior nasal quadrant was affected in the left.
His ophthalmologic examination was remarkable for right inferior disc swelling and left superior disc swelling.
Investigations
His blood work revealed evidence of systemic inflammation with mild normocytic anemia, moderate thrombocytosis, mild renal impairment, and elevated ESR and CRP. The MPO titre was within normal range.
MRI brain and orbit and lumbar puncture were normal.
Thought process
The lesion was localized to the optic nerve in this case, specifically the optic disc (or anterior segment of the optic nerve).
Given the acute onset of symptoms, a vascular etiology was considered most likely, which would give rise to the classical altitudinal visual disturbance owing to the vascular supply of the optic nerve. These findings would constitute the syndrome of anterior ischemic optic neuropathy.
Despite being more common, the arteritic form rather than the non-arteritic form should be the pathology at play given the background history and evidence of systemic inflammation.
Neurological manifestation of ANCA-associated vasculitis would be at the top of the differential list with giant cell arteritis as a close second as other clinical features of GCA were not present.
Outcome
High dose steroids was initiated. The rheumatology team was consulted. Temporal artery biopsy was suggested.