Factor XII (Hageman factor) deficiency

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Blood clots

Definition

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.

Symptoms

There are usually no symptoms.

Signs and tests

Factor XII deficiency is usually found when clotting tests are done for routine screening.

Tests may include:

• Factor XII assay
• Partial thromboplastin time (PTT)

Treatment

Treatment is generally unnecessary.

Expectations (prognosis)

The outcome is expected to be good without treatment.

Complications

There are usually no complications.

Calling your health care provider

This condition is usually discovered by the health care provider, when prolonged clotting is noticed in the process of running other laboratory tests.

Prevention

This is an inherited disorder. There is no known way to prevent it.

References

Kessler C. Hemorrhagic disorders: Coagulation factor deficiencies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 180.

Review Date: 3/2/2009

Reviewed 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.

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