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What

Factor XII deficiency is a rare, inherited, blood disorder that usually goes unnoticed until there are abnormalities in specific blood coagulation tests. While Factor XII levels can be dangerously low, most children with Factor XII deficiency do not have problems with excessive bleeding. Hageman Factor is a blood protein that participates in the blood clotting cascade, which is a chain reaction that is initiated when damage to a blood vessel occurs.

Who

Males and females are equally affected. The condition is more common in people of Asian descent. In 10% of the cases, parents of the affected person are related. It is estimated that the condition affects 2-3% of the general U.S. population.

Signs and Symptoms

Children with Factor XII deficiency may have any of the following: 1. Prolonged Partial Thromboplastin Time (PTT), which is a blood test 2. Rarely, blood clots (thrombi) can form at an early age. Blood clots can block the blood supply to the heart, brain or other organs, which can be dangerous. 3. Thrombophlebitis, which is inflammation of the vein at the site of a blood clot 4. Reduced levels of factor XII are associated with increased risk of multiple spontaneous abortions

Possible Causes

Factor XII deficiency is a hereditary condition that results from a defect in the Hageman Factor (HAF) gene located on chromosome 5. The condition is inherited in an autosomal recessive manner meaning that an affected child must inherit two copies (one from each parent) of the defective gene responsible for the Factor XII deficiency. The parents usually have one unaffected gene so they do not have Factor XII deficiency themselves, and there is no way to determine which gene gets passed on their offspring.

Diagnosis

The diagnosis of Factor XII deficiency is done by assessing the partial thromboplastin time (PTT) and measuring Factor XII levels. Upon finding a prolonged PTT and absent or low levels of Factor XII, the diagnosis can be confirmed.

Treatment

Since people with this condition are generally without symptoms, and excessive bleeding is not associated with HAF deficiency, no treatment is necessary. Close monitoring during periods of stress such as surgery or pregnancy is warranted.

Prognosis

People with this condition live a normal lifespan.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Bleeding Disorders Info Center: Factor XII Deficiency
Site offers a brief explanation about this condition.

Medline Plus
The site offers patient-oriented information about this blood test.

Canadian Hemophilia Society: Factor XII Deficiency
Good general information.

Google Search for Factor XII Deficiency

References and Sources

Goodnight, SH. and Hathaway, WE. (2001) Disorders of Hemostasis & Thrombosis. 2nd ed. pp. 154-157. Nathan, DG., Orkin, SH., Ginsburg, D., and Look, AT. (2003) Nathan and Oski’s Hematology of Infancy and Childhood. 6th ed. pp.136-137. OMIM: Hageman Factor Deficiency www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=234000 Technical information about the disease.