Summary
The clinical penetrance of venous thromboembolism (VTE) susceptibility genes is variable,
being lower in heterozygous carriers of factor V Leiden and prothrombin 20210A (mild
thrombophilia), and higher in the rare carriers of deficiencies of antithrombin, protein
C or S, and those with multiple or homozygous abnormalities (high-risk thrombophilia).
The absolute risk of VTE is low, and the utility of laboratory investigation for inherited
thrombophilia in patients with VTE and their asymptomatic relatives has been largely
debated, leading to the production of several Guidelines from Scientific Societies
and Working Groups. The risk for VTE largely depends on the family history of VTE.
Therefore, indiscriminate search for carriers is of no utility, and targeted screening
is potentially more fruitful. In patients with VTE inherited thrombophilia is not
scored as a determinant of recurrence, playing a minor role in the decision of prolonging
anticoagulation; indeed, a few guidelines consider testing worthwhile to identify
carriers of high-risk thrombophilia, particularly those with a family history of VTE.
The identification of the asymptomatic carrier relatives of the probands with VTE
and thrombophilia could reduce cases of provoked VTE, offering them primary antithrombotic
prophylaxis during risk situations. In most guidelines, this is considered justified
only for relatives of probands with a deficiency of natural anticoagulants or multiple
abnormalities. Counselling the asymptomatic female relatives of individuals with VTE
and/or thrombophilia before pregnancy or the prescription of hormonal treatments should
be administered with consideration of the risk driven by the type of thrombophilia
and the family history of VTE.
Keywords
Inherited thrombophilia - guidelines - venous thromboembolism - laboratory investigation
- familial investigation