[New causes of inherited thrombophilia]

Activated protein C resistance is the most frequent cause of thrombophilia. It is found in 20% of patients with an episode of deep vein thrombosis (DVT) and its prevalence in caucasian population is between 3-7%. Activated protein C resistance is secondary to an Arg 506 to Gln mutation of factor V (factor V Leiden). The relative risk of DVT for heterozygotes is 5 to 10, and for homozygotes 50 to 100. There is a 2- to 4-fold increase risk of recurrences in patients bearing the factor V Leiden mutation after a first episode of DVT. Recently a new mutation in the prothrombin gene (20210 G/A) was found to increase the relative risk of DVT by 2 to 4. Finally we also reviewed the association between DVT and hyperhomocysteinemia that is associated with a 2-fold increase risk of DVT.