THROMBOPHILIC GENOTYPES IN SUBJECTS WITH IDIOPATHIC ANTIPHOSPHOLIPID ANTIBODIES - PREVALENCE AND SIGNIFICANCE

To evaluate the significance of common thrombophilic genotypes in subj ects with idiopathic antiphospholipid antibodies (aPL) we determined t he methylenetetrahydrofolate reductase C-677-->T (MTHFR) and factor V A(506)-->G (FV Leiden) polymorphisms in 49 subjects with idiopathic aP L (57% of whom suffered spontaneous vein thrombosis), in 70 subjects w ith a history of spontaneous vein thrombosis and in 193 healthy subjec ts. The prevalence of MTHFR C-677-->T+/+ (homozygotes) was 25%, 18% an d 17% respectively amongst aPL thrombotics, non aPL thrombotics and co ntrols and that of MTHFR C-677-->T+/-(heterozygotes) was 53%, 59% and 53% respectively in the same groups. The prevalence of FV Leiden was h igher in aPL thrombotics (14% and in non aPL thrombotics (18%) than in controls (4%) (p less than or equal to = 0.05). APL thrombotics with MTHFR C-677-->T+/+ had a lower mean age at first thrombotic event (22 +/- 6 years) than aPL thrombotics with MTHFR C-677-->T+/- and non muta ted considered together (38 +/- 14 years, p = 0.0004) and than non aPL thrombotics with MTHFR C-677-->T+/+ (38 +/- 14 years, p = 0.003). FV Leiden may contribute to the hypercoagulability of a small, albeit sig nificant proportion of thrombotic aPL subjects, whereas the associatio n between MTHFR C-677-->T+/+ and aPL may have an impact on age at firs t occlusive event and suggests a possible pathogenetic interaction.