Combined factor V Leiden and prothrombin genotyping in patients presentingwith thromboembolic episodes

Background.-Several genetic defects are associated with increased risk of v enous thrombosis. The factor V Leiden (FVL) and prothrombin G20210A mutatio ns are the most frequent causes of inherited thrombophilia. Objectives.-To evaluate combined genotyping for these 2 mutations in patien ts presenting with thromboembolic episodes and to correlate genotypic findi ngs with clinical characteristics. Results.-Blood specimens were collected from 401 patients presenting with t hromboembolic disease between January 1998 and September 1998, and genotypi ng for both FVL and prothrombin mutations was performed. Thirty-two patient s (8%) were heterozygous for FVL, 4 (1%) were homozygous for FVL, and 20 (5 %) were heterozygous for the prothrombin mutation. Two cases (0.5%) were id entified with combined FVL and prothrombin mutations. The most common clini cal presentation was lower-extremity deep vein thrombosis with or without p ulmonary embolism. Arterial events were rare. The thromboembolic episodes w ere often precipitated by additional risk factors. Recurrent disease was fo und in 73.9% of FVL carriers and 52.9% of prothrombin mutation carriers; 52 % of the patients with FVL and 50% of prothrombin mutation carriers had a f irst thrombotic episode before age 45 years. The 2 cases with combined gene tic defects demonstrate amplified thrombotic risk. In the first case this w as effected in thrombosis at a young age, and recurrence of thrombotic even ts even in the absence of precipitating factors. A complex interplay betwee n genetic and additional risk factors was seen in the second case. Conclusions.-Identification of both FVL and prothrombin mutations is import ant in the overall assessment and management of patients with thrombophilia . Detection of these mutations can identify patients at high risk and help evaluate the interaction of genetic and acquired risk factors.