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Hereditary thrombophilia / hypercoagulopathies

Antithrombin deficiency

Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 19 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Hereditary deficiencies occur in 0.07 to 0.17% of general population
● Present in 1-9% of patients with venous thrombosis
● Higher risk for venous and arterial thrombosis than protein C or S deficiency or activated protein C resistance; overall 50% have thrombosis
● First thrombotic event occurs between ages 10-50 years
● Often occurs with other genetic or acquired risk factors
● Heterozygotes have levels 35-75% of normal

Genetics / types of mutations

● Many mutations exist (qualitative or quantitative)
● Usually autosomal dominant
● Homozygosity is very rare, usually incompatible with life due to neonatal thrombosis, except for those with a heparin-binding mutation subtype, who have severe thrombosis but may survive

Type I mutations: quantitative deficiency with 50% of normal levels; due to any of 80 point mutations
Type II mutations: dysfunctional protein; often asymptomatic
      ● IIa: mutations affect reactive site of target protease and heparin binding site
      ● IIb: mutations affect reactive site of target protease
      ● IIc: isolated decreased heparin binding

Acquired cause

● Acute hemolytic transfusion reaction
● Acute thrombotic episodes
● Burns (extensive)
● Heparin therapy
● Inflammatory bowel disease
● L-asparaginase therapy
● Liver disease
● Malignancy
● Malnutrition
● Nephrotic syndrome
● Plasmapheresis
● Preeclampsia
● Protein poor diet
● Thrombosis-recent or active (including DIC)


● Heparin (unfractionated or low molecular weight), followed by warfarin
● May need increased doses of heparin or antithrombin concentrates/fresh frozen plasma if resistant to heparin
● Should monitor antithrombin levels (should be 80-120%)

Additional references

Arch Pathol Lab Med 2002;126:1326, eMedicine #1, #2
Goodnight Jr, Scott & Hathaway, William (Eds) (2001). Disorders of hemostasis & thrombosis: A clinical guide. McGraw-Hill

End of Coagulation > Hereditary thrombophilia / hypercoagulopathies > Antithrombin deficiency

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