F12 deficiency; Hageman factor deficiency; Hageman trait; HAF deficiency
Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.
When you bleed, a series of reactions take place in the body that helps blood clots form. This process is called the coagulation cascade. It involves special proteins called coagulation or clotting factors. You may have a higher chance of excess bleeding if one or more of these factors are missing or are not functioning as they should.
Factor XII is one such factor. A lack of this factor does not cause you 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.
Exams and Tests
Factor XII deficiency is most often found when clotting tests are done for routine screening.
Tests may include:
- Factor XII assay to measure the activity of factor XII
- Partial thromboplastin time (PTT) to check how long it takes for blood to clot
- Mixing study, a special PTT test to confirm factor XII deficiency
Treatment is usually not needed.
The outcome is expected to be good without treatment.
There are usually no complications.
When to Contact a Medical Professional
The health care provider usually discovers this condition when running other lab tests.
This is an inherited disorder. There is no known way to prevent it.
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Hall JE. Hemostasis and blood coagulation. In: Hall JE, ed. Guyton and Hall Textbook of Medical Physiology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 37.
Ragni MV. Hemorrhagic disorders: coagulation factor deficiencies. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 174.