Definition of Factor XII (Hageman factor) deficiency:

Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.

Causes, incidence, and risk factors:

When you bleed, the body launches a series of reactions that help the blood clot. This is called the coagulation cascade. The process involves special proteins called coagulation factors. (Factor XII is a coagulation factor in this series of reactions.)

Each factor has a reaction that triggers the next reaction. The final product of the coagulation cascade is the blood clot.

A lack of factor XII does not cause the affected person to bleed abnormally, but the blood takes longer than normal to clot in a test tube.

Factor XII deficiency is a rare inherited disorder.