Factor XII

Factor XII (or Hageman factor) is a protein that in humans is encoded by the F12 gene. It is an enzyme of the serine protease (or serin endopeptidase) class. Factor XII is part of the coagulation cascade and activates Factor XI and prekallikrein in vitro.

Function

Factor XII is part of the coagulation cascade and activates Factor XI and prekallikrein in vitro. Factor XII itself is activated to factor XIIa by negatively charged surfaces, such as glass. This is the starting point of the intrinsic pathway. Factor XII can also be used to start coagulation cascades in laboratory studies.

Clinical significance

Deficiencies of Factor XII do not lead to hemorrhage, but excessive amounts can lead to thrombosis. Deficiencies can be detected by the activated partial thromboplastin time (aPTT) test—a prolonged aPTT suggests a deficiency of one of the factors. Factor XII deficiency is a rare disorder that is inherited in an autosomal recessive manner. This condition is usually discovered when prolonged clotting times are found on preoperative screening tests.

See also

• Coagulation
• Factor XI
• Thrombosis
• Hemorrhage

References

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External links

• Factor XII at WikiMD

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