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Hageman factor, also known as Factor XII, is a protein that plays a crucial role in the blood coagulation system, the kinin-kallikrein system, and the complement system, all of which are part of the body's immune response. It is named after Dr. Robert Hageman, who first identified the factor in the 1950s.

History

The Hageman factor was discovered in 1955 when a routine preoperative blood test on a patient named John Hageman revealed a prolonged partial thromboplastin time (PTT). Despite this, Hageman did not have a bleeding disorder, which led to further investigation and the discovery of the factor.

Function

Hageman factor is a serine protease (enzyme) that is synthesized in the liver. It is involved in the initiation of the intrinsic pathway of blood coagulation, which is activated when blood comes into contact with negatively charged surfaces. This can occur when blood vessels are damaged, exposing the underlying collagen.

In addition to its role in blood coagulation, Hageman factor also activates the kinin-kallikrein system and the complement system. The kinin-kallikrein system produces bradykinin, a peptide that causes blood vessels to dilate, and the complement system is a part of the immune system that helps to clear pathogens from the body.

Clinical significance

Mutations in the gene that encodes Hageman factor can lead to Factor XII deficiency, a rare disorder that is typically asymptomatic but can be associated with an increased risk of thrombosis. Conversely, high levels of Hageman factor have been associated with an increased risk of thromboembolism.

Hageman factor is also involved in the pathogenesis of hereditary angioedema, a rare genetic disorder characterized by episodes of severe swelling. In this condition, uncontrolled activation of the kinin-kallikrein system leads to excessive production of bradykinin, causing fluid to leak out of blood vessels and into tissues.

See also

• Blood coagulation
• Factor XII deficiency
• Hereditary angioedema