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Definition Return to top
Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.
Causes Return to top
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.
Symptoms Return to top
There are usually no symptoms.
Exams and Tests Return to top
Factor XII deficiency is usually found when clotting tests are done for routine screening.
Tests may include:
Treatment Return to top
Treatment is generally unnecessary.
Outlook (Prognosis) Return to top
The outcome is expected to be good without treatment.
Possible Complications Return to top
There are usually no complications.
When to Contact a Medical Professional Return to top
This condition is usually discovered by the health care provider, when prolonged clotting is noticed in the process of running other laboratory tests.
Prevention Return to top
This is an inherited disorder. There is no known way to prevent it.
References Return to top
Kessler C. Hemorrhagic disorders: Coagulation factor deficiencies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 180.Update Date: 3/2/2009 Updated by: 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.