The impact of the search for thrombophilia risk factors among antiphospholipid syndrome patients with thrombosis

Thrombosis is a major clinical feature of the antiphospholipid syndrome. In teractions between genetic and acquired factors could contribute to thrombo sis development. In this study, we evaluated 40 patients with antiphospholi pid syndrome and thrombosis, 31 primary and nine secondary to systemic lupu s erythemathosus, to estimate the carrier rates of factor V Leiden, 20210A --> G prothrombin variant and 677C --> T in the MTHFR gene. Protein C, prot ein S and antithrombin were measured in 30 patients, with a median of 100.6 6 +/- 23.86, 93.57 +/- 36.44 and 98.8 +/- 5.67%, respectively. None of the patients were deficient on these natural anticoagulants. No significant var iation was found between the patient group and the controls, regarding the prevalence of homozygotes for the mutated 677T allel (2.5 versus 5.4%), or heterozygotes for factor V Leiden (0 versus 0.7%). Despite the fact that th ese mutations are relatively common in Brazilian thrombophilc patients, its low prevalence in this cohort of patients suggest that these genetic alter ations are not risk factors for thrombosis in antiphospholipid syndrome. Th e prevalence of the mutated allele 20210A of the prothrombin gene was highe r in patients when compared with controls (5 versus 0.7%; P = 0.01), sugges ting that prothrombin variant could increase the risk of thrombosis in pati ents with antiphospholipid syndrome. Blood Coagul Fibrinolysis 11:679-682 ( C) 2000 Lippincott Williams & Wilkins.