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Coagulation

Hereditary thrombophilia / hypercoagulopathies

Prothrombin gene mutation (G20210A) / hyperprothrombinemia


Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 21 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

General
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● Mutation in G to A transition at nucleotide 20210 in 3 untranslated portion of prothrombin gene, which introduces a new Hind III site
● Associated with (may not directly cause) increased prothrombin levels, 2-5x increased risk of venous thrombosis
● Patients with G20210A mutation have increased levels of TAFI (Thrombin Activated Fibrinolysis I, a protein that inhibits clot lysis), which makes clots exist longer, leading to increased thrombotic episodes
● Risk is multiplicative if taking oral contraceptives and have factor V Leiden gene
● Heterozygous form occurs in 1-2% of normal individuals, 6-20% of patients with venous thrombosis
● Testing via nucleic acid based assay is preferred, as the lack of linearity of the clot-based Factor II assay at the high end makes this unsuitable for diagnostic use

Recommended patients to test
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● Patients with recurrent venous thromboembolic events
● First episode before age 50
● First unprovoked venous thromboemboli at any age
● Thromboses at unusual anatomic sites (cerebral, mesenteric, portal or hepatic veins)
● Venous thromboemboli in patient with first degree relative with venous thromboemboli before age 50 years
● Venous thromboemboli related to pregnancy or estrogen use, or unexplained pregnancy loss in second or third trimesters
● Young individuals with myocardial infarction and no other risk factors
● Also test factor V Leiden and other mutations (combination most clearly impacts clinical decision making)

Testing not recommended:
● As general population screen
● Routine test during pregnancy
● Routine test before or during oral contraceptive use or hormone replacement therapy
● As newborn initial test
● As initial test in patients with arterial thrombotic events

Treatment:
● Patients with thromboemboli and this mutation should receive similar treatment as other patients with venous thromboemboli

Additional references
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Arch Pathol Lab Med 2002;126:1319, Blood 2004;103:2157

End of Coagulation > Hereditary thrombophilia / hypercoagulopathies > Prothrombin gene mutation (G20210A) / hyperprothrombinemia


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