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. 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). The initial regimen comprised intravenous methylprednisolone (500 mg daily for 3 days) combined with 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. Regarding laboratory findings, the anti-streptolysin O (ASO) titer had also significantly improved, decreasing to 421 IU/mL. 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.
Wang et al. (Mon,) studied this question.