VWF and Arterial thrombosis: Also, since we have recently confirmed the association between genetic variation in STXBP5 and STX2 and VWF:Ag levels in young patients with a first event of arterial thrombosis [7], we hypothesized that genetic variation in STXBP5 and STX2 may also affect VWF:Ag levels in patients diagnosed with type 1 VWD according to the current ISTH guidelines.