Acute Retinal Necrosis or Lymphoma?

Purpose To describe an atypical presentation of primary vitreoretinal lymphoma (PVRL) mimicking acute retinal necrosis (ARN) and to identify its initial findings that argue against necrotizing viral retinitis.Methods Observational case report with clinical and imaging assessment, aqueous humor polymerase chain reaction (PCR), and diagnostic pars plana vitrectomy with cytologic, immunophenotypic and molecular analysis.Results A 74-year-old woman presented with progressive visual decline in the left eye (LE). Slit-lamp examination revealed diffuse granulomatous keratic precipitates with inferior coalescence and mild anterior chamber inflammation, without ciliary injection, posterior synechiae, raised intraocular pressure or pain. Fundus visualization was limited by dense vitreous haze. Ultra-widefield imaging demonstrated poorly defined whitish retinal lesions suggestive of necrotizing retinitis. B-scan ultrasonography showed marked vitreous heterogeneity with an attached retina, and optical coherence tomography (OCT) demonstrated hyperreflective material located between the retinal pigment epithelium and Bruch membrane. Infectious workup, including PCR for Herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Toxoplasma gondii, was negative. No antiviral therapy was administered. Diagnostic vitrectomy revealed atypical CD20-positive lymphoid cells with MYD88 L265P mutation and an elevated interleukin-10/interleukin-6 ratio, confirming PVRL.Conclusion PVRL may closely mimic ARN, particularly in unilateral cases with granulomatous features. In this eye, three findings argued against necrotizing viral retinitis: massive keratic precipitates without ocular congestion, retinal lesions lacking the peripheral circumferential pattern of ARN, and sub-retinal pigment epithelial infiltration on OCT. All were available at the first visit despite severe media opacity, and should shorten the interval to vitreous biopsy.