Prothrombin mutation test

Clinical significance

A point mutation has been described in the gene coding for prothrombin (a protein that promotes clot formation, and therefore thrombosis), consisting of the replacement of a guanine with an adenine (G20210A variant).
This mutation is associated with an increase of about 30% in plasma prothrombin levels. It is inherited in an autosomal dominant pattern: carriers have a one in two chance of passing the predisposition on to their children.
The G20210A genetic variant has a prevalence of 3-5% in Europe, increasing from north (2-5%) to south (3-7%), while it is very rare in Africa and Asia. It is present in about 10% of unselected patients with venous thrombosis, and in 18% of people with thrombosis or selected because of family history. Homozygotes are extremely rare. Heterozygotes have about 3 times the risk of the general population of developing venous thrombosis, while homozygotes have 80 times the risk of non-carriers. In heterozygotes the risk of heart attack appears to be increased about 5 times in women and 1.5 times in men.