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Overview of Coagulation Disorders
Abnormal bleeding can result from disorders of the coagulation system (see Overview of Hemostasis), of platelets, or of blood vessels. Disorders of coagulation can be acquired or hereditary. The major causes of acquired coagulation disorders are vitamin K deficiency (see Vitamin K Deficiency), liver disease, disseminated intravascular coagulation, and development of circulating anticoagulants. Severe liver disease (eg, cirrhosis, fulminant hepatitis, acute fatty liver of pregnancy) may disturb hemostasis by impairing clotting factor synthesis. Because all coagulation factors are made in the liver, both the PT and PTT are elevated in severe liver disorders. (PT results are typically reported as INR.) Occasionally, decompensated liver disease also causes excessive fibrinolysis and bleeding due to decreased hepatic synthesis of α 2 -antiplasmin.
The most common hereditary disorder of hemostasis is von Willebrand disease (see Von Willebrand Disease) The most common hereditary coagulation disorders are the hemophilias.
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