Persistent central retinal vein occlusion (CRVO) in protein S and C4b complement deficiency.

A late-adolescent female presented with sudden-onset, painless diminution of vision in her left eye, with multiple treatment interventions and recurrences of symptoms, over one year. She was diagnosed with left eye central retinal vein occlusion (CRVO) and was given eight intravitreal anti-vascular endothelial growth factor (VEGF) (ranibizumab) injections elsewhere, with only transient improvement followed by recurrence of retinal haemorrhages and macular oedema. Considering her young age and absence of typical risk factors, a detailed infectious, autoimmune and hematologic workup was performed. A detailed thrombophilia panel revealed reduced free protein S activity (14%) and C4b complement levels, indicating an inherited thrombophilic state. A history of recurrent pregnancy loss in her grandmother hinted at a prothrombotic predisposition. She was started on oral warfarin and injected with two additional anti-VEGF injections to manage existing macular edema. Her visual acuity remained stable with no recurrence of macular oedema over a one-year follow-up, highlighting the importance of comprehensive evaluation in young CRVO patients and importance of systemic therapy in combination with ocular therapy in successful clinical management and sustained outcomes.