 A number of conditions that have been linked with venous thrombosis are possibly genetic and possibly acquired . These include : elevated levels of factor VIII , factor IX , factor XI , fibrinogen and thrombin @-@ <unk> fibrinolysis inhibitor , and decreased levels of tissue factor pathway inhibitor . Activated protein C resistance that is not attributable to factor V mutations is probably caused by other factors and remains a risk factor for thrombosis . 
