The risk of symptomatic pulmonary embolism due to proximal deep venous thrombosis differs in patients with different types of inherited thrombophilia.

It is uncertain whether the presence of inherited thrombophilia influences the risk of developing symptomatic pulmonary embolism (PE) and whether different thrombophilic alterations are associated with different risks of symptomatic PE. To investigate such issue, we retrospectively studied 920 patients with proximal deep vein thrombosis (DVT) of the legs with or without symptomatic PE referred for thrombophilia screening; patients with overt cancer or antiphospholipid antibodies had been excluded. Three hundred fifty-four patients (38.5%) had deficiency of antithrombin (AT, n = 16), protein C (PC, n = 26), protein S (PS, n = 22), factor V Leiden (FVL, n = 168), prothrombin G20210A (PT-GA, n = 87), or multiple abnormalities (n = 35), and 566 had none of the studied thrombophilic abnormalities. Symptomatic PE complicated the first DVT in 242 patients (26%); the risk of PE was increased in patients with AT deficiency (relative risk [RR] 2.4, 95% confidence interval [CI] 1.6-3.6) or with PT-GA (RR 1.5, 95%CI 1.1-2.0) and decreased in those with FVL (RR 0.7, 95%CI 0.5-1.0) in comparison with those with unknown inherited defect. These data suggest that patients with proximal DVT have different risks of symptomatic PE according to the type of inherited thrombophilia.