Prothrombin 20210 Gene Mutation

The Prothrombin 20210 gene mutation is caused by a G to A transition in the 3'-untranslated region of the prothrombin (Factor II) gene at position 20210. This condition is associated with mild increases in plasma prothrombin levels and an increased risk of venous thrombosis.

This condition is found in approximately 10% of patients presenting with venous thromboembolism and about 1% of the normal population. Carriers of the 20210A allele have an approximately 2.8-fold increased risk of venous thrombosis and there is some evidence that it also increases the risk of stroke and cerebral vein thrombosis.

As with the FV Leiden mutation, the presence of the Prothrombin 20210 mutation may substantially increase the risk of thrombosis in association with other congenital (FV Leiden, Protein C or S deficiency) or acquired (pregnancy, estrogen therapy, Lupus Anticoagulants, hyperhomocysteinemia) risk factors.

Diagnosis of the Prothrombin 20210 gene mutation must be made through specifc genetic testing (e.g. PCR), which can also reveal whether the patient is heterozygous or homozygous for the condition. Although most affected individuals do have elevation of the plasma Factor II clotting activity, we do not recommend this as a screening test for the Prothrombin 20210 gene mutation.