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. When one or more of these clotting factors are missing, there is usually a higher chance of bleeding.
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.
There are usually no symptoms.
Signs and tests
Factor XII deficiency is usually found when clotting tests are done for routine screening.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.