A Challenging Case: When Retinal Findings May Tell the Whole Story

To report a rare case of isolated immune-mediated retinal arteriolar vasculitis with fluorescein angiography (FFA) findings raising suspicion for Susac syndrome, without systemic involvement.

A 19-year-old woman presented with a sudden inferotemporal scotoma in her left eye, along with a history of headaches and subtle emotional disturbances. A comprehensive ophthalmologic and systemic evaluation was performed, including multimodal retinal imaging, brain MRI, tonal audiometry, and extensive laboratory testing to assess infectious, inflammatory, neoplastic, and thromboembolic causes. Treatment with high-dose corticosteroids and mycophenolate mofetil was initiated. Clinical course and treatment response were monitored through serial imaging.

Fundus examination and FFA revealed retinal arteriolar narrowing, Gass plaques, and arteriolar wall hyperfluorescence (AWH), consistent with a microangiopathic process. Brain MRI and audiometry were unremarkable, and systemic and infectious workup was negative. Based on these findings, the patient was diagnosed with isolated immune-mediated retinal vasculitis. Due to the presence of AWH, Susac syndrome was considered as a possible diagnosis, although the presentation was incomplete. Corticosteroid tapering led to symptom recurrence and the development of a new ischemic lesion, which resolved with continued immunosuppression. The patient remained asymptomatic on maintenance therapy.

This case highlights the diagnostic challenges of isolated retinal arteriolar vasculitis and the importance of recognizing a typical presentations of Susac syndrome. AWH on FFA is an important, though non-pathognomonic, diagnostic clue. In such cases, a broad differential diagnosis should be considered. Early immunosuppressive therapy and close follow-up are essential to preserve visual function and detect potential systemic progression.