title: Delayed-onset HIT caused by low-molecular-weight heparin manifesting during fondaparinux prophylaxis.
abstract: Heparin-induced thrombocytopenia (HIT) is a prothrombotic condition caused by platelet-activating antibodies that react with platelet factor 4 (PF4)/heparin complexes. Delayed-onset HIT occurs after heparin is stopped. Fondaparinux, a synthetic pentasaccharide, is thought to be a safe alternative anticoagulant in HIT. We describe a patient with delayed-onset HIT triggered by low-molecular-weight heparin (LMWH) which occurred during fondaparinux prophylaxis and which was complicated by microangiopathic hemolytic anemia. Patient serum contained high-titer anti-PF4/heparin antibodies demonstrating heparin-dependent platelet activation with serial dilutions. Confirmed delayed-onset HIT with LMWH has not been previously reported. Low dose fondaparinux does not necessarily prevent thrombotic complications of HIT.
authors.affiliation: Department of Medicine, Michael G. DeGroote School of Medicine McMaster University, Hamilton, Ontario, Canada.
authors.forename: Khalid A
authors.initials: KA
authors.lastname: Alsaleh
authors.forename: Sami M A
authors.initials: SM
authors.lastname: Al-Nasser
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Bates
authors.forename: Ameen
authors.initials: A
authors.lastname: Patel
authors.forename: Theodore E
authors.initials: TE
authors.lastname: Warkentin
authors.forename: Donald M
authors.initials: DM
authors.lastname: Arnold
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D001323:Autoantibodies / Q000097:blood*; D001792:Blood Platelets / Q000276:immunology; D005260:Female; D005343:Fibrinolytic Agents / Q000009:adverse effects*; D000077425:Fondaparinux; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology; D011134:Polysaccharides / Q000627:therapeutic use; D013921:Thrombocytopenia / Q000139:chemically induced*
chemical_list: D000925:Anticoagulants; D001323:Autoantibodies; D005343:Fibrinolytic Agents; D006495:Heparin, Low-Molecular-Weight; D011134:Polysaccharides; D010978:Platelet Factor 4; D000077425:Fondaparinux