To describe demographic and clinical characteristics of vascular involvement in patients with Behçet's syndrome (BS) and to evaluate associations with such involvement.

We retrospectively evaluated records of 2118 BS patients. In total, 460 patients diagnosed with superficial thrombophlebitis (ST) and/or major vascular events (venous and/or arterial involvements) were included in current analysis. Isolated ST with no accompanying deep venous thrombosis might be accepted as part of skin involvement; therefore, we defined two different outcomes for vascular involvement (“any vascular event” and “major vascular events”) and performed univariable and multivariable logistic regression to assess factors associated with these outcome variables.

Overall, 68 (14.8%) patients had isolated ST, and 392 (85.2%) had major vascular events. The mean age of vascular BS was 33.8 (SD: 10.5) years and median follow-up was 13.9 (Q1–Q3: 8.3–22.9) years. The primary sites of major vascular events were deep venous thrombosis (n=358, 77.8%), pulmonary arterial involvement (n=66, 14.3%), extrapulmonary arterial involvement (n=52, 11.3%), and intracardiac thrombosis (n=14, 3.0%), respectively. Male sex was significantly associated with a higher risk for both outcome variables. When it was added to analysis, ST itself was the strongest explanatory variable that was associated with major vascular events in all multivariable models (ORs=11.9, 12.0, 13.0, and 18.9). While HLA-B51 was significantly associated with any vascular event, there was no similar observation for major vascular events.

Male sex is a well-known risk factor for major vascular events in BS, but our study established that presence of ST was the strongest risk factor.