What is the prothrombin gene mutation?

The prothrombin gene G20210A mutation differs from the gene for normal prothrombin or factor II by a single nucleotide (nucleotides are the building blocks of DNA). This mutation causes the body to produce excess amounts of prothrombin. Consequently, in individuals with the prothrombin gene mutation, prothrombin levels are higher, which in turn contributes to the formation of blood clots.

Individuals who have inherited one copy of the gene (heterozygotes) have a risk of DVT or PE similar to the risk of individuals who have inherited one copy of the factor V Leiden gene.

Individuals who have inherited two copies of the prothrombin gene mutation (homozygotes) or individuals who have inherited one copy of the prothrombin gene mutation and one copy of the factor V Leiden (compound heterozygotes) have a risk of DVT or PE similar to the risk of individuals who have inherited two copies of the factor V Leiden gene.

The percentage of people who have the prothrombin gene depends on the population studied. As with factor V Leiden, higher percentages are reported among people of European descent compared to people from other continents. In the United States, the prothrombin gene mutation has been found in 1 to 2 percent of Americans of European ancestry and fewer Americans of other ancestry.

Mike’s story:

After my DVT and bilateral PEs, I was put on a regimen of heparin and Coumadin® and went through three lysis procedures (with clot-busting or thrombolytic drugs) for the DVT by the interventional radiologist. Each time the procedures went extremely well, and the popliteal and common femoral veins were cleared of the clots. Even though I stayed on heparin and Coumadin, the clots came back. The results of the lysis procedures were very disappointing, and I will be on Coumadin for the rest of my life.

Later, it was determined that I had a genetic blood disorder. I am heterozygous for the prothrombin gene mutation, which I inherited from my father’s side of the family.