Objectives Behçet’s disease (BD) is a chronic systemic vasculitis. Thrombosis is a frequent and life-threatening complication. The pathogenesis of BD is poorly understood and evidence supporting a role for primed neutrophils in BD-associated thrombotic risk is scant. To respond to inflammatory insults, neutrophils release web-like structures, known as neutrophil extracellular traps (NETs), which are prothrombotic. We evaluated the role of NETs and markers of NETs in BD.

Methods Blood samples were collected from patients with BD, according to the International Study Group Criteria for Behçet's disease, and healthy donors (HD). NET components, including cell-free DNA (CfDNA) and neutrophil enzymes myeloperoxidase (MPO), were assessed in serum or in purified neutrophils from patients with BD and HD.

Results Patients with active BD had elevated serum cfDNA levels and MPO-DNA complexes compared with patients with inactive BD and to HD. In addition, levels of cfDNA and MPO-DNA complexes were significantly higher in patients with BD with vascular involvement compared with those without vascular symptoms. Purified neutrophils from patients with BD exhibited spontaneous NETosis compared with HD. Thrombin generation in BD plasma was significantly increased and positively correlated with the levels of MPO-DNA complexes and cfDNA. Importantly, DNAse treatment significantly decreased thrombin generation in BD plasma but not in HD plasma. In addition, biopsy materials obtained from patients with BD showed NETs production in areas of vasculitic inflammation and thrombosis.

Conclusions Our data show that NETs and markers of NETS levels are elevated in patients with BD and contribute to the procoagulant state. Targeting NETs may represent a potential therapeutic target for the reduction or prevention of BD-associated thrombotic risk.