The tendency for abnormal blood clotting is known as thrombophilia (hypercoagulable state). A blood clot (thrombus) is important to stop us bleeding to death when we cut ourselves but in a person with the condition (thrombophiliac) the clotting process (thrombosis, coagulation) is out of control and causing a blood clot to form inside an unbroken blood vessel. If left unchecked it can lead to the loss of blood supply to tissues beyond the clot which then become damaged - sometimes with fatal consequences.

The commonest cause of thrombophilia is Hereditary Resistance to Activated Protein C (HRAPC, APC). A mutation in the factor V gene, Factor V Leiden, leads to slowed inactivation of the factor V molecule by it's inhibitor, Protein C. About 1 in 20 healthy people carry this genetic defect and therefore have a higher risk of thrombosis. Other congenital causes of thrombophilia include Anti-Thrombin III Deficiency, Protein C Deficiency and Protein S Deficiency.

Diagnosis of thrombophilia, for both thrombosis sufferers and non-sufferers alike, is useful for guiding lifestyle choices. For example in women with the APC gene defect it is known that oral contraceptives can increase the risk of venous thrombosis 35-fold. Smoking is also known to slow down blood flow and contributes to the risk of thrombosis. Trauma and prolonged periods of rest, such as during air travel or after surgery, can also increase risks.

A Blood Clot By Any Other Name

There are many medical phrases associated with blood clots:

  • thromboembolism (embolism) - is a blood clot in a vein or artery
  • thrombophlebitis (phlebitis) - inflammation of a vein when a blood clot forms
  • neonatal purpura fulminans - in a newborn - is a blood clot on the skin
  • deep vein thrombosis (DVT) - is a blood clot in the leg
  • pulmonary embolism (PE) - is a blood clot on the lung
  • stroke (cerebrovascular accident) - is a blood clot on the brain
  • heart attack (coronary thrombosis) - is a blood clot in the heart
    • myocardial infarcation - with death of heart tissue
    • myocardial ischaemia - with reduction of blood supply
Last updated: Thursday, 1st August 2013, © 2000-2017

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