Evaluation Of Factor V Leiden, Prothrombin Mutations and The Homozygous mutation 677T In The MTHFR Gene In Patients With  Venous Thrombosis

Over the last few years there has been increased interest in laboratory tests for thrombophilia. Testing is predominantly performed to identify asymptomatic individuals at risk for a first thrombosis or patients (pts) at risk of relapse. The results are not always concordant, and the impact on clinical practice is not yet defined, especially for heterozygous forms.

We evaluated heterozygous and homozygous Factor V Leiden (FVL) and prothrombin (FII) mutations and the homozygous C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in 98 pts with venous thrombosis distinguishing idiopathic forms from forms that are secondary to malignancy, surgery, forced immobilization or hormone treatments.

FII mutation was present in 17% of idiopathic and 5.8% of secondary forms. FVL mutation was present in respectively 17% and 15.8% and MTHFR homozygous state in 31.9% and 21.5%. At least one of FII or FVL mutations was present respectively in 31.9% and 19%, at least one of the three mutations examined was present in 57.4% and 36.2%.

In pts with limb venous thrombosis (n-64), the percentages for each mutation are respectively: FII-23.5% and 6.6%, FVL-20.5% and 6.6%, MTHFR 35.2% and 16.6% .At least one mutation between FII and FVL is present respectively in 42.1% and 13.3% (P = 0,028) while at least one of the three mutations is present in 61.7% and 30.5% (P = 0,022)

In our pts with pulmonary thromboembolism (n-36) FII mutation was absent while FVL mutation was present in 7.6% of idiopathic and 21.7% of the secondary thrombosis, MTHFR in 30.7% and in 30.4%. At least one of the three examined mutations was present in 38.4% and 47.8%.

The mutations we have studied are generally more frequent in idiopathic forms. The difference reaches statistical significance in limb venous thrombosis where they seem to have a significant relevance, although in a heterozygous state, and to promote thrombosis even in absence of other causes.

In pulmonary thromboembolism (PTE) pts FII mutation was absent, FVL mutation is less frequent in pts with idiopathic thrombosis and MTHFR homozygous state is equivalent between the two subgroups. Thus, they seem to not influence PTE pathogenesis that would be likely sought in different causes.