II. Epidemiology

  1. Rare cause of Thrombophilia
  2. First episode of thrombosis occurs ages 10-30 years

III. Pathophysiology

  1. Antithrombin III (AT3) is a Glycoprotein produced by the liver
    1. Antithrombin III Deficiency (AT3 Deficiency) is an inherited Autosomal Dominant trait (or may be acquired)
    2. Heterozygous AT3 Deficiency patients have 25-50% AT3 functional levels
  2. Antithrombin III (AT3) normally inhibits clotting, Coagulation Factors (enhanced by Heparin)
    1. Factor IXa
    2. Factor Xa
    3. Factor XIa
    4. Factor XIIa
    5. Thrombin
  3. Antithrombin III Deficiency results in Thrombophilia
    1. Deep Vein Thrombosis
    2. Pulmonary Embolism

IV. Causes

  1. Inherited Antithrombin III Deficiency (most common)
  2. Acquired Causes
    1. Liver Failure
    2. Malnutrition
    3. Nephrotic Syndrome (AnticoagulationProtein loss including AT3)

V. Labs

  1. Functional level Antithrombin III

VII. Complications

  1. Recurrent Miscarriage
  2. Venous Thromboembolism (DVT, PE)
    1. Up to 50% lifetime Prevalence (esp. in teen years during hormonal increases)

VIII. References

  1. Jean-Louis and Sethuraman (2023) Crit Dec Emerg Med 37(7): 4-11

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