Acquired Thrombin Inhibitor in a Patient with Liver Cirrhosis

Abstract
An unusual thrombin inhibitor is described in a patient suffering from liver cirrhosis, associated with a polyclonal gammopathy. In all screening tests that are based on thrombin action, the plasma clotting time was prolonged; in contrast, a test using the thrombin-like enzyme thrombin coagulase was not influenced. A specific thrombin inhibitor, present in the patient’s plasma, was assumed. Fractionation experiments showed that the inhibitor was associated with the patient’s IgG fraction. The IgG fraction dose-dependently inhibited the action of thrombin on fibrinogen and the inhibition of thrombin by antithrombin III, but the amidolytic activity of thrombin was only little affected.
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