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Definition:
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Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.
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Causes, incidence, and risk factors:
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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.
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Symptoms:
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There are usually no symptoms.
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Signs and tests:
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Factor XII deficiency is usually found when clotting tests are done for routine screening.
Tests may include:
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Treatment:
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Treatment is usually not needed.
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Expectations (prognosis):
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The outcome is expected to be good without treatment.
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Complications:
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There are usually no complications.
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Calling your health care provider:
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The health care provider usually discovers this condition after noticing prolonged clotting in the process of running other laboratory tests.
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Prevention:
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This is an inherited disorder. There is no known way to prevent it.
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References:
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Gailani D, Neff AT. Rare coagulation factor deficiencies. In: Hoffman R, Benz EJ Jr, Shattil SJ, et al, eds. Hoffman Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone Elsevier;2008:chap 127.
Kessler C. Hemorrhagic disorders: Coagulation factor deficiencies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 180.
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