Resistance to activated protein C in unselected patients with arterial and venous thrombosis

Elena M. Faioni, Cristina Razzari, Ida Martinelli, Daniela Panzeri, Franca Franchi, Pier Mannuccio Mannucci

Research output: Contribution to journalArticlepeer-review


Four hundred and ninety-three consecutive patients referred for arterial or venous thrombosis were screened for congenital and acquired abnormalities of blood coagulation predisposing to thrombosis, end were compared to 341 age- and sex-matched controls. The aim of the study was to determine the prevalence and clinical characteristics of resistance to activated protein C (APC), a defect shown to have different prevalences in different ethnic groups and to be associated with an increased risk of thrombosis. Seventy- three (15%) patients had both APC resistance and the 1691 G to A factor V gone mutation, compared to 6/341 (2%) controls. Seven patients had antithrombin deficiency (1.4%), 11 had protein C deficiency (2.2%), and 4 had protein S deficiency (0.8%). The relative risk of thrombosis in APC-resistant patients was 9.4. Resistance to APC was associated mainly with venous thrombosis, the moat frequent being deep-vein thrombosis of the lower limbs. Fifty-eight percent of APC-resistant patients had an associated risk factor at the first thrombotic event: pregnancy and oral contraceptive intake were associated with the first thrombotic episode in 35% and 30% of women, respectively. APC resistance is the most frequent defect of blood coagulation in the general population and in the unselected thrombotic population studied by us.

Original languageEnglish
Pages (from-to)59-64
Number of pages6
JournalAmerican Journal of Hematology
Issue number2
Publication statusPublished - Jun 1997


  • Antithrombin
  • APC resistance
  • Protein C
  • Protein S
  • Thrombosis

ASJC Scopus subject areas

  • Hematology


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