Thrombophilia is a predisposition to the formation of thrombosis. Its cause may be inherited or acquired.

1) Inherited causes of thrombophilia include:
  • Protein C deficiency
  • Protein S deficiency
  • Antithrombin deficiency
  • Activated protein C resistance
  • Factor V Leiden (see below)
  • Homocysteinuria

2) Acquired causes of thrombophilia include:
  • cancer
  • pregnancy
  • eostrogen therapy
  • sickle cell disease
  • thrombotic thrombocytopenic purpura (see below)
  • nephrotic syndrome
  • antiphospholipid antibodies

Factor V Leiden

A point mutation on the gene for clotting factor V results in a variant known as 'factor V Leiden'.
The result of this mutation is that factor V is insensitive to protein C inactivation, resulting in hypercoagulabilty and hence increased risk of PEs/DVTs and even Budd Chiari syndrome.

Factor V Leiden is inherited in an autosomal dominant fashion with incomplete penetrance.

Thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura is a condition in which systemic thrombi develop formed of platelets and Von Willebrand factor
The 5 key features are:
  • Thrombocytopenic purpura
  • Microangiopathic haemolytic anaemia
  • Renal failure
  • Fever
  • Fluctuating neurological dysfunction

Thrombotic thrombocytopenic purpura may be either:
  • Congenital = mutation of ADAMTS13 allelle (AKA Upshaw-Schulman syndrome)
  • Acquired = autoantibodies against ADAMTS13

Adult females are most commonly affected

Treatment is:
  • Plasma exchange
  • Second line therapies include: vincristine, splenectomy, cyclosporine, azothioprine
  • Possibly rituximab
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