The non-classical risk factors associated with CRVO in the younger population include hypercoagulable states (polycythemia, protein C or protein S deficiency, antiphospholipid syndrome, collagen vascular disease, myeloproliferative disorder), syphilis, sarcoidosis, Behcet’s disease, and HIV infection [2,3,5]. Here, PROS1 is linked to Behcet disease.