Superficial Venous Thrombosis: Prevalence of Common Genetic Risk Factors and Their Role on Spreading to Deep Veins

Abstract

Conclusion: There is a high presence of genetic mutations (factor V Leiden, prothrombin G20210A mutation, and 5,10-methylenetetrahydrofolate reductase [MTHFR C677T]) in patients with superficial venous thrombosis (SVT) occurring in normal veins. Summary: SVT that occurs in varicose veins is considered of low clinical relevance because of the generally favorable outcome. SVT occurring in so-called healthy veins represents only approximately 25% of all SVT. This type of SVT is generally considered of greater clinical relevance because it has been associated with various neoplastic conditions. It is also known that SVT occurring in so-called healthy veins can progress into the deep system. Depending on the study, propagation into deep veins is about 3% to 15%. Genetic abnormalities of coagulation can also predispose to SVT. Less well studied is whether the presence of a genetic coagulation abnormality occurring in patients with SVT predisposes them to progression into the deep system. In this study the authors evaluated 107 patients with SVT and no other obvious risk factors. They used ultrasound examinations to document progression into the deep system and tested for the presence of factor V Leiden, prothrombin G20210A mutation, and MTHFR C677T mutations. In the patients with SVT in normal veins, factor V Leiden was present in 26.3% when the thrombus was limited to the superficial veins and was present in 60% of SVT that extended into the deep system. Prothrombin gene mutation was found in 7.9% of SVT limited to the superficial system and in 20% where SVT progressed to the deep system. MTHFR C677T mutation was found in 23.7% of patients with SVT limited to the superficial system and in 40% where SVT progressed to the deep system. In patients with SVT occurring in varicose veins, the presence of these abnormalities was less common (6.7%, 4.4%, and 6.7% respectively). If, however, the SVT from the varicose veins spread to the deep system, prevalence of genetic abnormalities was considerably higher (13.5% factor V Leiden mutation, 7.4% prothrombin gene mutation, and 21.4% MTHFR C677T mutation). Comment: This article paper provides guidance on which patients with SVT should undergo a thrombophilia evaluation. Whereas patients with SVT occurring in normal veins were previously recognized as having a reasonably high incidence of genetic coagulation abnormalities, this report points out that those patients who have SVT in varicose veins that extends into the deep system have a significant prevalence of genetic abnormalities as well. SVT patients appropriate for thrombophilia workup are those where the SVT occurs in normal veins and those with SVT in varicose veins that extends into the deep system.