So far, none of the thrombophilic factors were shown to be associated with the thrombotic tendency observed in BS.52,55–59 A defect in fibrinolysis was however suggested.60,61 Gul et al previously reported that coagulation factor V gene G1691A mutation (factor V Leiden), could contribute to thrombotic complications in BS patients with deep vein thrombosis.62 However, this was not confirmed.56,63,64 The current data indicates that the pathogenesis of thrombosis in BS is not due to a coagulation abnormality. Here, F5 is linked to Bloom syndrome.