ABSTRACT

January 2005

Section 5 Hematology

Thrombosis, excessive blood clotting involving vascular inflammation, is the result of endothelial injury, decrease in blood flow, and an imbalance among procoagulant and anticoagulant factors. This chapter reviews areas to address when assessing patients with thrombotic disorders, including age at onset; presence or absence of a provoking factor, such as surgery or trauma; family history; recurrent thrombosis; and site of thrombosis. A section on extent and timing of the hypercoagulable workup offers recommendations based on clinical-assessment results. The discussion highlights the epidemiology, pathophysiology, clinical presentation, diagnosis, and treatment of hereditary hypercoagulable states, including antithrombin-III deficiency, protein C and protein S deficiency, factor V Leiden, and hyperhomocysteinemia, as well as acquired hypercoagulable states, such as antiphospholipid antibody syndrome, heparin-induced thrombocytopenia (HIT) and thrombosis, Trousseau syndrome, and thrombotic reactions to estrogens. Also reviewed are rare or poorly established disorders, including dysfibrinogenemia and dysplasminogenemia, and risk factors such as prothrombin gene mutation 20210A; lipoprotein(a); and elevated fibrinogen, factor VII, and factor VIII levels. Figures illustrate the metabolism of factor V Leiden and of homocysteine and the proposed mechanism for HIT. Tables summarize inherited and acquired hypercoagulable states, screening tests for hypercoagulable states, clinical features that suggest thrombophilia, frequency and relative risk of venous thrombosis in selected hypercoagulable states, proposed clinical and laboratory criteria for the antiphospholipid antibody syndrome, classification of antiphospholipid antibodies, and guidelines for managing patients with venous thromboembolism. This chapter contains 147 references.

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