Prothrombin (factor II), an important factor in coagulation, a group of proteins produced by the liver that are activated in sequence (cascade) when a blood vessel is injured. The result of the coagulation cascade is the formation of a blood clot, which creates a barrier in the area of the lesion and protects it until it heals. The synthesis of prothrombin (factor II) by the liver is controlled by a gene present in two copies in the cell. Normal individuals have two copies of the gene without mutation (wild GG-type homozygous). Others have one copy (heterozygous) or very rarely two copies (homozygous) of the gene with a modification (mutation) called “G20210A”. Prothrombin G20210A is associated with a 2.5 to 3 times greater risk of clot formation in veins (phlebitis, etc.).
The potential risk posed by the presence of this mutation varies from one person to another. Some individuals will never develop venous thromboses. In individuals who have had one or more clot formations, the presence of this mutation is likely the cause. If they do not have this mutation, the formation of these clots is likely due to another cause.