Frosted Branch Angiitis Associated with Streptococcal Infection: A Case Report
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Background Frosted branch angiitis (FBA) is a rare retinal vasculitis characterized by diffuse perivascular sheathing that resembles frosted branches. This condition is classified into masquerade, frosted branch response, and idiopathic forms. Streptococcal infection is a recognized but infrequent trigger for FBA. We present a novel case of bilateral FBA associated with serologically confirmed streptococcal infection, which demonstrated a rapid response to combined corticosteroid and antibiotic therapy. Case presentation A 45-year-old male presented with acute bilateral vision loss occurring three days after an upper respiratory infection. On initial examination, best-corrected visual acuity (BCVA) was 0.25 in the right eye and 1.0 in the left eye. Fundoscopy revealed bilateral frosted branch-like perivascular sheathing with retinal hemorrhages. Fluorescein angiography (FFA) revealed optic disc hyperfluorescence and intense perivascular leakage, along with widespread capillary non-perfusion, particularly in the nasal periphery of the right eye. Serological testing showed a significantly elevated anti-streptolysin O titer of 619 IU/mL. The patient was diagnosed with streptococcal-associated secondary FBA (Kleiner Type II). Treatment was initiated with intravenous methylprednisolone (500 mg daily) and oral azithromycin (500 mg daily). Within three days, BCVA in the right eye improved to 0.8, and vitreous haze resolved. At the one-month follow-up, BCVA had fully recovered to 1.0 in both eyes, with near-complete resolution of vascular sheathing on fundoscopy and normalized macular architecture on optical coherence tomography. Conclusions This case demonstrates that streptococcal infection can trigger bilateral FBA. Early intervention with combined immunosuppressive and antimicrobial therapy led to complete visual recovery. We recommend serial anti-streptolysin O testing and close ophthalmic monitoring in cases of post-infectious retinal vasculitis.
