title: Increased sensitivity of factor IX to phenprocoumon as a cause of bleeding in a patient with antiphospholipid antibody associated thrombosis.
abstract: We report one patient who presented with a spontaneous bleeding complication under phenprocoumon therapy. Oral anticoagulation was initiated due to deep-vein thrombosis which was attributed to an antiphospholipid antibody syndrome. Coagulation analysis revealed a strong and selective reduction of factor IX (F IX) activity to 1%, whereas the other vitamin K-dependent factors (II, VII, X), the prothrombin time and International Normalized Ratio (INR) were within the therapeutic range. After withdrawal of phenprocoumon, all vitamin K-dependent factors including F IX normalized. Because the patient suffered from a recurrence of thrombotic events, he was re-exposed to phenprocoumon and the disproportionate decline of F IX was observed again. These findings indicate an increased sensitivity of F IX to vitamin K antagonists, representing an uncommon mechanism associated with bleeding complications under oral anticoagulant treatment.
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University of Bonn, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Harbrecht
authors.forename: J
authors.initials: J
authors.lastname: Oldenburg
authors.forename: P
authors.initials: P
authors.lastname: Klein
authors.forename: D
authors.initials: D
authors.lastname: Weber
authors.forename: J
authors.initials: J
authors.lastname: Rockstroh
authors.forename: P
authors.initials: P
authors.lastname: Hanfland
mesh_terms: D000328:Adult; D017152:Antibodies, Antiphospholipid / Q000097:blood*; D000925:Anticoagulants / Q000009:adverse effects*; D001778:Blood Coagulation Disorders / Q000097:blood / Q000139:chemically induced*; D001779:Blood Coagulation Factors / Q000187:drug effects; D005164:Factor IX / Q000187:drug effects*; D006801:Humans; D008297:Male; D010644:Phenprocoumon / Q000009:adverse effects*; D011517:Prothrombin Time; D013927:Thrombosis / Q000188:drug therapy* / Q000276:immunology*; D013997:Time Factors
chemical_list: D017152:Antibodies, Antiphospholipid; D000925:Anticoagulants; D001779:Blood Coagulation Factors; D005164:Factor IX; D010644:Phenprocoumon