Тромбофилия F2\F5 Leiden (G20210A\G1691A), кровь

Factor V (F5) G1691A (Arg506Gln) mutation analysis—commonly referred to as the Factor V Leiden test—assesses inherited resistance to activated protein C and the resulting predisposition to thrombophilia. The assay supports evaluation of venous thromboembolism (including deep vein thrombosis and pulmonary embolism), particularly in patients with events at a young age or with recurrent episodes. It also informs risk assessment in pregnancy (e.g., preeclampsia and thromboembolic complications) and guides counseling before initiating combined oral contraceptives or hormone replacement therapy. Results are interpreted in the context of genetic, clinical, and laboratory data. Co-inheritance with other prothrombotic variants, including prothrombin 20210G and MTHFR C677T, is associated with higher thrombotic risk, earlier onset, and more severe events.

Hemostasis is maintained by coordinated procoagulant, anticoagulant, and fibrinolytic pathways that preserve blood fluidity yet enable rapid control of bleeding. Disruption of this equilibrium increases the likelihood of hemorrhage or thrombosis. Hereditary thrombophilia is common and frequently unrecognized, most often manifesting as deep vein thrombosis and venous thromboembolism. Variants in coagulation factor genes—most notably F2 (G20210A) and F5 (G1691A)—play a central role in these disorders. The F5 gene encodes coagulation factor V, a plasma protein that circulates in an inactive form and is converted by thrombin, in the presence of calcium, to the active cofactor Va. Factor Va accelerates the factor Xa–mediated conversion of prothrombin to thrombin. The canonical F5 G1691A substitution produces an Arg506Gln change in one of three cleavage sites for the natural anticoagulant activated protein C, resulting in impaired inactivation of factor Va and increased thrombin generation (activated protein C resistance). The mutation follows an autosomal dominant pattern; a single altered allele can increase thrombotic risk. Clinical expression varies with age, environmental exposures, and additional genetic changes. Triggers include pregnancy, use of oral contraceptives, hormone replacement therapy, prolonged immobilization, and smoking. Epidemiologic observations highlight both prevalence and clinical impact. Among pregnant individuals with a history of venous thromboembolism, the prevalence of Factor V Leiden was 43.7% versus 7.7% in healthy controls (Gerhardt et al., 2000). Co-carriage with MTHFR C677T or prothrombin 20210G further elevates risk and is linked to earlier and more severe thrombotic events. An association with ischemic stroke has been reported (Casas et al., 2004). The A-allele frequency ranges from 1% to 8% across populations. An evolutionary advantage—reduced bleeding during childbirth—has been proposed to explain its persistence despite potential adverse effects. Early identification permits targeted prophylaxis and treatment to mitigate cardiovascular and pregnancy-related thromboembolic complications.