Definition

Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.

Alternative Names

F12 deficiency; Hageman factor deficiency; Hageman trait; HAF deficiency

Causes

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.

Symptoms

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

Treatment is usually not needed.

Support Groups

More information and support for people with factor XII deficiency and their families can be found at:

• National Hemophilia Foundation -- www.hemophilia.org/bleeding-disorders-a-z/types/other-factor-deficiencies/factor-xii
• National Organization for Rare Disorders -- rarediseases.org/rare-diseases/factor-xii-deficiency/
• NIH Genetic and Rare Diseases Information Center -- rarediseases.info.nih.gov/diseases/6558/factor-xii-deficiency

Outlook (Prognosis)

The outcome is expected to be good without treatment.

Possible Complications

There are usually no complications.

When to Contact a Medical Professional

The health care provider usually discovers this condition when running other lab tests.

Prevention

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

References

Gailani D, Benjamin TF, Wheeler AP. Rare coagulation factor deficiencies. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 135.

Hall JE, Hall ME. Hemostasis and blood coagulation. In: Hall JE, Hall ME, eds. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 37.

Ragni MV. Hemorrhagic disorders: coagulation factor deficiencies. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 165.