The Congenital Hypercoagulable Disorders

Antithrombin Deficiency

Antithrombin is a serine protease inhibitor of thrombin and also inhibits factors IXa, Xa, XIa, and XIIa. Thrombin is irreversibly bound by antithrombin and prevents throm-bin's action on fibrinogen, on factors V, VIII, and XIII, and on platelets.6 This anticoagulant is synthesized in the liver and endothelial cells, and has a half-life of 2.8 days.7 Antithrombin deficiency has a prevalence of 1 : 5000 with more than 100 genetic mutations and an autosomal dominant inheritance pattern.8 Homozygotes typically die in utero whereas heterozygotes typically have an antithrombin level that is 40 to 70% of normal.

Antithrombin deficiency is associated with lower extremity venous thrombosis as well as mesenteric venous thrombosis, and there are two clinical types. Individuals with Type

I deficiency have a reduced number and function of anti-thrombin, and individuals with Type II have normal production but a reduction in function. Additionally, the heparin binding site of the antithrombin may be mutated.9 The risk of thrombosis increases as the functional antithrombin activity decreases to less than 80% of normal levels. The highest risk for thrombosis occurs when the activity is less than 60% of normal.1

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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