title: Resistance to activated protein C in unselected patients with arterial and venous thrombosis.
abstract: 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, and 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 gene 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 most 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.
authors.affiliation: Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, I.R.C.C.S. Maggiore Hospital and Institute of Internal Medicine, University of Milan, Italy.
authors.forename: E M
authors.initials: EM
authors.lastname: Faioni
authors.forename: C
authors.initials: C
authors.lastname: Razzari
authors.forename: I
authors.initials: I
authors.lastname: Martinelli
authors.forename: D
authors.initials: D
authors.lastname: Panzeri
authors.forename: F
authors.initials: F
authors.lastname: Franchi
authors.forename: P M
authors.initials: PM
authors.lastname: Mannucci
mesh_terms: D000328:Adult; D000368:Aged; D001778:Blood Coagulation Disorders / Q000503:physiopathology*; D003276:Contraceptives, Oral / Q000009:adverse effects; D004789:Enzyme Activation; D005165:Factor V / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic; D011486:Protein C / Q000378:metabolism*; D020151:Protein C Deficiency; D018455:Protein S Deficiency / Q000150:complications; D012307:Risk Factors; D013927:Thrombosis / Q000503:physiopathology*
chemical_list: D003276:Contraceptives, Oral; D011486:Protein C; D005165:Factor V