I. Genetic abnormalities.
1, antithrombin deficiency.
2, congenital abnormal fibrinogenemia.
3, thrombomodulin.
4, homocysteinemia.
5, anticardiolipin antibodies.
6, fibrinogen activation inhibitor overdose.
7, Prothrombin 20210A mutation Protein C deficiency.
8, V Leiden factor (APC-R).
9, fibrinogen deficiency.
10, abnormal fibrinogenemia.
11, Protein S deficiency.
12, Ⅻ factor deficiency.
II. predisposing factors.
1, trauma/fracture.
2, Stroke.
3, advanced age.
4, central venous catheter.
5, chronic venous insufficiency.
6, smoking.
7, Pregnancy, postpartum period.
8, Crohn’s disease.
9, nephrotic syndrome.
10, hyperviscosity.
11, platelet abnormalities Surgical procedures.
12, braking.
13, malignancy ± chemotherapy.
14, obesity.
15.Heart failure.
16, long-distance travel.
17.Oral contraceptives.