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Gwen - Haematology > Inherited and Acquired Thrombophilia > Flashcards

Inherited and Acquired Thrombophilia Flashcards

1
Q

What is thrombophilia?

A

Thrombophilia is a term describing inherited or acquired defects of haemostasis leading to a predisposition to venous or arterial thrombosis.

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2
Q

What is part of the thrombophilia screen?

A
  • PT, APTT
  • Fibrinogen
  • Lupus Anticoagulant
  • Anti-cardiolipin antibodies
  • Antithrombin activity
  • Protein C activity
  • Free protein S antigen
  • Factor VII activity
  • Activated Protein C Resistance Factor V Leiden genotype
  • Prothrombin genotype
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3
Q

Why is pregnancy a hypercoagulable state?

A
  • Resistance to activated protein C
  • Protein S activity decreases
  • Fibrinogen and Factors II, VII, VIII, X increases
  • Levels and activity of fibrinolytic inhibitors increase
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4
Q

What are the main inherited thrombophilias?

A
  • Activated protein C resistance/Factor V Leiden
  • Protein C and S deficiency
  • Antithrombin deficiency
  • Prothrombin variant (gene mutation)
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5
Q

What is Factor V Leiden?

A

Activated protein C resistance

Factor V Leiden differs from normal factor V by a single nucleotide substitution (Arg506Gln). This variation makes factor V less likely to be cleaved by activated protein C. As factor V is a cofactor for thrombin generation impaired inactivation by activated protein C results in a tendency to thrombosis.

Sooooo a mischapen factor 5 not degraded by activated C (autsommal dominant)

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6
Q

How much does the thrombotic risk increase in someone with Factor V Leiden who is on oral contraceptive pill?

A

35-fold increase

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7
Q

How much does the thrombotic risk increase in someone with Factor V Leiden who is on oral contraceptive pill?

A

35-fold increase

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8
Q

What is a prothrombin variant?

A

A mutation in the 3′ untranslated region of the prothrombin gene, which is associated with elevated levels of prothrombin and a 2–3-fold increase in the risk of venous thrombosis. There is also down-regulation of fibrinolysis, due to thrombin activated fibrinolysis inhibitor

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9
Q

How is factor V Leiden inherited?

A

Autosomal dominant inheritence

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10
Q

What is Protein C/Protein S deficiency?

A

These vitamin K-dependent factors act together to cleave and neutralize factors V and VIII. Heterozygote deficiency for either protein risk thrombosis. Autosommal dominant.

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11
Q

How is protein C and S deficiency inherited?

A

Autosomal dominant

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12
Q

Where are protein C and S synthesised?

A

Liver

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13
Q

What are acquired causes of protein C or S deficiency?

A
  • Liver disease
  • Severe infection/septic shock/DIC
  • Postoperative state
  • Pregnancy/OCP
  • Acute thromboembolic disease
  • Nephrotic syndrome
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14
Q

Why is prenancy a hypercoaguable state?

A
  • Resistance to actived protein C in 2nd and 3rd trimester
  • Protein S decreases activity
  • Increased of fibrinogen factrs 2, 7, 8 and 10
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15
Q

What is Antithrombin III deficiency?

A

Antithrombin is a co-factor of heparin, and inhibits thrombin. Deficiency leads to uninhibited thrombin production. Recurrent thrombotic episodes occur starting at a young age in the inherited variety. Patients may be relatively resistant to heparin as antithrombin is required for its action.

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16
Q

What are those with Antithrombin III deficiency resistant to?

A

Heparin - acts using antithrombin

17
Q

What are the acquired causes of thrombophilia?

A
  • Antiphospholipid syndrome
  • Heparin induced thrombocytopenia
  • Malignancy
  • Nephrotic syndrome
18
Q

What antibodies are found in antiphospholipid syndrome?

A
  • Anti-cardiolipin
  • Lupus anticoagulant
19
Q

What is antiphospholipid syndrome?

A

Patients who have thrombosis (arterial or venous) and/or recurrent miscarriages and who also have persistently positive blood tests for antiphospholipid antibodies (aPL) have the antiphospholipid syndrome (APS).

Negatively charged phospholipids and β2-glycoprotein I are present on the outer surface of apoptotic blebs and so aPLs are believed to arise by a similar mechanism to the lupus autoantibodies. Pathogenic aPLs bind to the N-terminal domain of β2-glycoprotein I and this interaction is facilitated when the protein is bound to phospholipid on the surface of cells such as endothelial cells, platelets, monocytes and trophoblasts. This alters the functioning of those cells leading to thrombosis and/or miscarriage.

20
Q

What are features of antiphospholipid syndrome?

A
  • Venous thrombosis
  • Areterial thrombosis
  • Thrombocytopenia
  • Recurrent miscarriage
21
Q

What is heparin induced thrombocytopenia?

A

An uncommon complication of heparin therapy and usually occurs 5–14 days after first heparin exposure. It is due to an immune response directed against heparin/platelet factor 4 complexes. All forms of heparin have been implicated but the problem occurs less often with LMW heparins.

HIT is paradoxically associated with severe thrombosis.

Note: common to get a slight dip platelets on itnitiation of herparin (non-immune)

Suspect if: new onset thrombocytopenia, plts reduced by 50%, thrombosis, necorisis @ injection site.

Accelerated cross linking of platelets and removal from circulation

22
Q

How long does it normally take for heparin induced thrombocytopenia to occur after starting heparin?

A

Approximately 10 days

23
Q

What should you do if someone develops heparin induced thrombocytopenia?

A
  • Stop all heparins
  • Non-heparin anticoagulant
24
Q

When would you investigate someone for suspected thrombophilia (i.e. thrombophilia screen)?

A
  • Those presenting with venous thrombosis at an early age (<40) and who are from apparent VTE prone families
  • Children with purpura fulminans
  • Pregnant women at risk of venous thrombosis
25
Q

When would you not investigate someone for causes of thrombophilia?

A

Do not offer if:

  • Patients who are continuing anticoagulation treatment
  • Patients who have had provoked DVT or PE
  • First-degree relatives of people with a history of DVT or PE and thrombophilia.
26
Q

What are causes of a hypercoagulable state?

A
  • Malignancy
  • Pregnancy/post-partum
  • Oestrogen therapy eg. OCP
  • Trauma/surgery to lower extremity
  • IBD
  • Nephrotic syndrome
  • Sepsis
  • Thrombophilia
27
Q

What are causes of circulatory stasis which can predispose to thrombosis?

A
  • AF
  • LV systolic dysfunction
  • Immobility
  • Venous insufficiency - varicose veins
  • Venous obstruction - pelvic tumour, obesity, pregnancy
28
Q

What are causes of vessel damage that can lead to thrombosis?

A
  • Trauma/surgery
  • Venepuncture
  • Chemical irritation
  • Heart valve disease/replacement
  • Atherosclerosis
  • Indwelling lines – cannula, central line

Gwen - Haematology (33 decks)

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