Definition

Factor XII deficiency is an inherited disorder with no symptoms. Factor XII is a protein involved in blood clotting. A deficiency of this factor does not cause abnormal bleeding in the affected person, but the blood takes longer than normal to clot in a test tube.

Causes, incidence, and risk factors

Factor XII deficiency is a rare hereditary disorder. It is usually found when clotting tests are done for routine screening. It is not associated with abnormal bleeding.

Symptoms

There are usually no symptoms.

Signs and tests

• Abnormal factor XII assay
• Prolonged partial thromboplastin time

Treatment

Treatment is generally unnecessary.

Support Groups

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.

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References

McPherson RA and Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa.: WB Saunders; 2006.

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philladelphia, Pa: Churchill Livingston; 2005:2089-90.

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