DOMMR

1. DOMMR Week of 9/28-10/1

2. Objectives Discuss hypercoaguable states Focus specifically on the inherited hypercoaguable conditions Briefly describe the mechanism behind each of the inherited thrombophilias Review the hypercoaguable workup and when it is appropriately done

3. Venous Thromboembolism Most common presentation is DVT of the lower extremity and PE A risk factor for thromboembolism is found in 80% of patients Often more than one factor at play Divided into hereditary and acquired

4. Table 1. Inherited and Acquired Causes of Venous Thrombosis.Table 1. Inherited and Acquired Causes of Venous Thrombosis.

5. Inherited Thrombophilias In the recent past, a genetic cause for thrombophilia was detected in only 5-15% of patients Limited to antithrombin gene deficiency, protein C+S deficiency, dysfibrogenemia 1993: Discovered Factor V gene mutation (Factor V Leiden) 1996: Discovered the prothrombin G20210A gene mutation Inherited thrombophilias are most common in Caucasians, rare in African or Asian In all comers with DVT, the incidence of inherited thrombophilias is 24-37% Of Caucasian patients who present with initial symptomatic DVT, 12-20% are heterozygous for factor V Leiden and 6% heterozygous for prothrombin G20210A mutation

6. Inherited Thrombophilias Inherited hypercoaguable states A genetic tendency for venous thromboembolism Should be suspected in anyone who: Presents with an unprovoked venous or arterial thromboembolic disease at <45 yrs 2 or more thrombotic episodes in the absence of a risk factor for thrombosis History of objectively confirmed idiopathic thrombosis in first-degree relative Thrombosis in an unusual site Mesenteric veins, dural sinus Neonatal thromobosis or stroke History of recurrent fetal loss

7. Inherited thrombophilias Will often present with DVT or PE More than 50% of cases, thrombosis is provoked by surgery, pregnancy, immobilization, OCP, HRT, or old age Recurrent venous thrombosis is highest in deficiency of antithrombin, protein C, protein S, greater than one inherited thrombophilia, homozygous for factor V Leiden Those heterozygous for factor V Leiden and prothrombin gene mutation have not been shown to have a higher rate of recurrent venous thrombosis verses the general population

8. Figure 1. Major Mechanisms Involved in the Normal Control of Coagulation and Inherited Thrombophilias. Control of coagulation is achieved by the protein C pathway and antithrombin. In the protein C pathway thrombin bound to thrombomodulin activates protein C, which in turn inactivates activated factor V and factor VIII in the presence of protein S, thereby down-regulating the generation of thrombin. The neutralization of thrombin is achieved by antithrombin bound to heparin sulfate. In the inherited thrombophilias, a deficiency of antithrombin, protein C, or protein S, aberrant activity of factor V, or increased activity of prothrombin results in decreased neutralization of thrombin or increased generation of thrombin.Figure 1. Major Mechanisms Involved in the Normal Control of Coagulation and Inherited Thrombophilias. Control of coagulation is achieved by the protein C pathway and antithrombin. In the protein C pathway thrombin bound to thrombomodulin activates protein C, which in turn inactivates activated factor V and factor VIII in the presence of protein S, thereby down-regulating the generation of thrombin. The neutralization of thrombin is achieved by antithrombin bound to heparin sulfate. In the inherited thrombophilias, a deficiency of antithrombin, protein C, or protein S, aberrant activity of factor V, or increased activity of prothrombin results in decreased neutralization of thrombin or increased generation of thrombin.

10. Factor V Leiden Factor V is activated to Va, which acts as a cofactor in the conversion of prothrombin to thrombin Normally, Factor Va is degraded by APC and limits prothrombin conversion to thrombin Arginine is replaced by Glutamine (Arg506Gln) on the factor V gene, resulting in a protein called factor V Leiden Factor V Leiden is less susceptible to inactivation by APC and is now considered “resistant to APC” This results in a prothrombotic state

11. Factor V Leiden Most common - 40-50% of inherited thrombophilias Found in 5% of the Caucasian population Found in 10-20% of patients with first episode of idiopathic DVT Found in 50% of patients with recurrent DVT 90-95% of those with factor V Leiden are heterozygous Homozygotes have a more severe course Acquired forms of APC resistance found in pregnancy, use of OCPs, elevated Factor VIII or those with antiphospholipid antibodies

12. Factor V Leiden Anticoagulation therapy Long term therapy not recommended in heterozygotes At no higher risk of recurrent thrombosis than those without the mutation In homozygotes, should use prophylaxis in high risk settings Heterozygous, pregnant women with no history of thrombosis are at low risk for thrombosis Anticoagulation is not recommended Recommendations differ if have a history of thrombosis or if Pt is homozygous

14. Prothrombin G20210A Mutation A Vitamin K-dependant protein synthesized in the liver Due to substitution of adenine for guanine Results in 30% higher prothrombin levels This promotes generation of thrombin and impairs inactivation of Factor Va by APC Found in 2% of the Caucasian population Seen in 6-10% of patients presenting with first episode of unprovoked DVT Like with factor V Leiden, there is no increased risk of recurrent DVT in those with the mutation

15. Enhances activity of Protein CEnhances activity of Protein C

16. Protein C deficiency Vitamin K-dependant protein made by the liver Many different gene mutations are found on the Protein C gene Among those with mutations on the Protein C gene, levels of Protein C vary widely Some heterozygotes actually have normal levels Homozygotes manifest shortly after birth with neonatal purpura fulminans Heterozygotes are prone to venous thrombosis, but not at increased risk for arterial thrombosis 20% develop thrombosis by 30yrs, 50% by 50yrs 20% develop thrombosis by 30yrs, 50% by 50yrs

17. Protein C deficiency -  Warfarin induced skin necrosis Seen in heterozygotes when giving large loading doses of warfarin and heparin not given concomitantly Occurs within days of starting therapy and develops over fatty tissue (thigh, buttocks, breasts) or extremities Begins as a painful erythematous lesion and leads to necrosis Occurs because of the shorter half life of Protein C verses the other vitamin K-dependent proteins As a result, protein C levels decrease rapidly once warfarin therapy has been initiated (reduced to 50% of normal within one day) This effect is even more pronounce in Protein C deficiency Protein C is lost before the anticoagulant effects of warfarin are established and thrombosis develops

18. Protein C deficiency Warfarin induced skin necrosis Treatment: stop warfarin, give heparin, Vitamin K, protein C concentrate Can restart warfarin once skin lesions resolve, restart in low doses and give with heparin

20. Protein S Deficiency Vitamin K-dependant protein Circulates as both a free protein (40%) and bound C4b-binding protein (60%), which is part of the classic complement system Only free Protein S can act as a cofactor to APC for the inhibition of Factors Va and VIIIa C4b is increased in acute phase reactions, causing free Protein S to be decreased Like in Protein C deficiency, homozygous patients present soon after birth with neonatal purpura fulminans Protein S is a Vitamin K dependent protein, so levels will be reduced in patients on warfarin Therefore, must discontinue warfarin therapy at least 1 week prior to testing for deficiency Protein S is a Vitamin K dependent protein, so levels will be reduced in patients on warfarin Therefore, must discontinue warfarin therapy at least 1 week prior to testing for deficiency

21. Protein S Deficiency Decreased levels of Protein S in Liver disease Renal disease Women – especially those on OCPs or pregnant IBD Neonates, infants 50% of heterozygotes experience DVT by 35yrs May have atypical presentation: migraine headache, mesenteric vein thrombosis

23. Antithrombin III Deficiency A vitamin K-independent protein that works inhibit thrombin Prevalence: 1:2000-1:5000 persons 30% of heterozygotes develop a thrombosis by 30yrs, 65% by age 50yrs Homozygous deficiency is almost always incompatible with life 60% will have recurrent thrombosis Risk of thrombosis is particularly high in pregnancy Heparin prophylaxis recommended throughout pregnancy and coumadin for 6 weeks postpartum

24. Testing for hypercoaguable states Acquired and genetic causes frequently overlap What tests should be ordered? When should they be ordered? Will the duration of anticoagulation be affected?

25. Testing for Hypercoaguable States In some settings, up to 50% of Pts with new thrombosis are found to have an abnormality that predisposes to thrombosis This would suggest routine screening may be of benefit Patients with factor V Leiden and prothrombin gene G20210A mutation do not have an elevated risk of recurrent thrombosis when compared to patients with venous thromboembolism without the mutation Currently there are no recommendations to routinely screen for Factor V Leiden or prothrombin gene mutation (the 2 most common inherited disorders) On the other hand, testing for Protein C and S deficiency and antithrombin deficiency may be warranted because there is an increased risk of recurrent thrombosis after anticoagulation is discontinued

26. Hypercoaguable workup In the setting of acute clot or therapy: Coumadin reduces protein C and S levels Heparin can reduce antithrombin levels Heparin and coumadin make testing for lupus anticoagulant and APC unreliable Sepsis is associated with reduction in levels of protein C, protein S, antithrombin

27. Hypercoaguable workup APC resistance screen Clotting assay, then confirm with a genetic test Prothrombin G20210A mutation Genetic test (PCR) Functional assay for Protein C + S, antithrombin III deficiency Heterozygous deficiencies are from many different mutations and abnormalities Measure both free and total Protein S Affected by acute thrombosis and anticoagulation, so check levels at least 2 weeks after completing therapy Anticardiolipin and lupus anticoagulant clotting assay Testing should be done at least 2 weeks after completion of anticoagulation

28. Table 3. Diagnostic Tests for Thrombophilias.Table 3. Diagnostic Tests for Thrombophilias.

29. Figure 2. Approach to the Diagnosis and Treatment of Thrombophilia in Patients with Venous Thrombosis. Panel A shows the clinical evaluation of the likelihood of thrombophilia, initial anticoagulant therapy, and the performance of tests. Panel B shows the criteria for continuing therapy and for prophylaxis.Figure 2. Approach to the Diagnosis and Treatment of Thrombophilia in Patients with Venous Thrombosis. Panel A shows the clinical evaluation of the likelihood of thrombophilia, initial anticoagulant therapy, and the performance of tests. Panel B shows the criteria for continuing therapy and for prophylaxis.

30. Review Thrombosis due to acquired and inherited causes: **Factor V Leiden Less susceptible to inhibition of APC “Resistant to APC” **Prothrombin gene mutation Protein C deficiency Protein S deficiency Antithrombin III deficiency

31. Figure 1. Major Mechanisms Involved in the Normal Control of Coagulation and Inherited Thrombophilias. Control of coagulation is achieved by the protein C pathway and antithrombin. In the protein C pathway thrombin bound to thrombomodulin activates protein C, which in turn inactivates activated factor V and factor VIII in the presence of protein S, thereby down-regulating the generation of thrombin. The neutralization of thrombin is achieved by antithrombin bound to heparin sulfate. In the inherited thrombophilias, a deficiency of antithrombin, protein C, or protein S, aberrant activity of factor V, or increased activity of prothrombin results in decreased neutralization of thrombin or increased generation of thrombin.Figure 1. Major Mechanisms Involved in the Normal Control of Coagulation and Inherited Thrombophilias. Control of coagulation is achieved by the protein C pathway and antithrombin. In the protein C pathway thrombin bound to thrombomodulin activates protein C, which in turn inactivates activated factor V and factor VIII in the presence of protein S, thereby down-regulating the generation of thrombin. The neutralization of thrombin is achieved by antithrombin bound to heparin sulfate. In the inherited thrombophilias, a deficiency of antithrombin, protein C, or protein S, aberrant activity of factor V, or increased activity of prothrombin results in decreased neutralization of thrombin or increased generation of thrombin.

32. Review Factor V Leiden and antithrombin gene mutation are not associated with recurrent thrombosis Protein C deficiency associated with warfarin induced skin necrosis Protein S is both free and bound (to C4b binding protein) Only free protein C can act as a cofactor for APC Elevated levels of C4b in sepsis, acute phase reactions Testing should be done after 2 weeks after therapy is concluded (which is typically 6 months) Decreased levels of Protein C, Protein S, and Antithrombin with acute clot and with treatment

33. Follow Up of patient Was given 6 months of coumadin Will get high priority (APC resistance, Factor V Leiden gene mutation, prothrombin gene mutation) and intermediated priority testing (protein C deficiency, protein S deficiency, antithrombin III deficiency) 2 weeks after anticoagulation is stopped