[Factor V Leiden and activated protein C resistance].

Factor V Leiden is characterised by a point mutation which prevents the physiologic inhibition of activated factor V by activated protein C (Activated Protein C Resistance). This mutation is now considered as the most frequent inherited thrombophilic disorder. It is found in about 20% of patients with venous thrombotic disease, far before ATIII, Protein C and S deficiency. Its prevalence (4% in the general belgian population, 1 to 15% in Europa) allows frequent associations with other thrombophilic disorders, inherited or acquired, such as contraceptive pill. Biological testing are now ready for screening, but the opportunity of a systematic evaluation in front of a risk situation remains a matter to discussion.