Inherited Thrombophilia (Blood Clotting Disorder)

Approximately one in every thousand individuals will experience abnormal clotting in their lives. One cause of abnormal clot formation is genetic, which means a person has inherited a gene from their parents that predisposes them to abnormal clotting. The medical term for this inherited abnormal tendency to clot is known as inherited thrombophilia.
Over the past decade a number of genes have been found to be associated with inherited thrombophilia.

Factor V Leiden

An inherited mutation of the Factor V gene, known as Factor V Leiden, is found in approximately 5% of Caucasian (Anglo-Celtic) people. Patients with the Factor V Leiden mutation will be at higher risk of experiencing a clot in their veins than others in the community. In fact the Factor V Leiden mutation is found in approximately 15% of all patients with first time clots. Furthermore, the mutation is found in 40% of young people, and 60% of pregnant women with venous clots.

The Factor V Leiden mutation is also associated with increased complications during pregnancy, such as high blood pressure (pre-eclampsia), recurrent miscarriage, stillbirth and pulmonary embolism, a blood clot from another part of the body that travels to the lungs. Women who have one copy of this mutation and are taking oral contraceptives have an even higher risk of the formation of blood clots in their veins.

Prothrombin 20,210

Another gene associated with increasing risk of abnormal clotting in the veins is called Prothrombin or Factor II. The DNA change that leads to the increased risk is known as Prothrombin 20,210. This DNA change is found in only 1-2% of Caucasians and in up to 8% of patients experiencing their first venous clot.

Lifetime risk increase for developing a venous clot

Who should be tested ?

1. People who have recurrent thrombosis
2. People with vein clots in unusual sites
3. Pregnant women with venous thrombosis
4. Women on oral contraception who experience venous thrombosis
5. People younger than 50 years of age who experience venous thrombosis
6. People who have relatives with the Factor V Leiden or Prothrombin 20,210 mutations.
7. Women with recurrent pregnancy loss
8. Spontaneous venous thrombosis
9. Other Family members - Family members of people who are known to carry these mutations are also advised to seek testing.

Treatment

Preventative treatment can be instigated during periods of increased risk, such as surgery, pregnancy or immobility. Also people at risk can avoid risk factors such as smoking, oestrogen therapy and oral contraception.