PURPOSE: Behçet disease is a systemic disease of young adults characterized by 
venous occlusion in both the deep venous and retinal circulations. In severe 
ocular disease, blindness may occur despite immunosuppressive treatment. The 
most common inherited risk factor for the development of idiopathic venous 
thrombosis is the presence of the Factor V (FV Leiden) mutation, which confers 
resistance to activated protein C. The association of FV Leiden with Behçet 
disease has been reported, but its influence on ocular disease is not known. We 
therefore investigated the prevalence of this mutation in patients with Behçet 
disease to determine its contribution to the presence and severity of ocular 
disease.
METHODS: One hundred and six Middle Eastern patients satisfying international 
criteria, and 120 healthy control subjects without a history of venous 
thrombosis were included in the study, and patients underwent standard 
examination by two ophthalmologists with an interest in Behçet disease. Genomic 
DNA was extracted from peripheral blood leukocytes and screened for the FV 
Leiden mutation with the polymerase chain reaction method with sequence-specific 
primers (PCR-SSP).
RESULTS: FV Leiden was detected in 19% (23/120) of the control population 
compared with 27% (29/106) of all patients with Behçet disease (P = .13). 
However, among patients with Behçet disease who had ocular disease (75/106), the 
prevalence of FV Leiden was significantly higher (32%) than it was in control 
subjects (P = .04). Furthermore, ocular patients with Behçet disease in whom 
retinal occlusive disease was observed (25/75) had the highest expression of FV 
Leiden (44%).
CONCLUSIONS: These data suggest that FV Leiden may be an additional risk factor 
for the development of ocular disease and, in particular, retinal 
vaso-occlusion, and it may contribute to the poor visual outcome in these 
patients.