Factor XI deficiency, also called factor 11 deficiency or hemophilia C, is an inherited disorder which is usually mild but can cause uncontrolled bleeding. This bleeding tends to be more severe after surgery, injury, or childbirth. Bleeding can be a particular problem after tooth extraction, dental surgery, tonsil surgery, or urinary tract surgery.
People with factor XI deficiency may also be prone to bruising, nosebleeds, or blood in their urine. Rarely, male children with the disease will bleed heavily following circumcision. More than half of women with the disease have abnormally heavy and prolonged menstrual periods.
It is uncommon for people with factor XI deficiency to bleed spontaneously for no obvious reason. There may be a delay in bleeding following an injury.
Factor XI is a protein produced by the liver and found in the blood. It helps platelets in the blood to clot following an injury to a blood vessel. In people with factor XI deficiency, levels of factor XI are lower than normal. Bleeding problems tend to occur when factor XI levels are lower than 15% of the normal level. Bleeding problems can occur, however, when levels are as high as 70% of the normal level. The severity of the bleeding varies widely from person to person, even among members of the same family.
Carriers of factor XI deficiency are at elevated risk for bleeding problems. Studies have suggested that 20 to 50% of carriers of the disease show "excessive bleeding," although the definition of this phrase varies. Rarely, carriers have shown major bleeding problems.
Factor XI deficiency is fairly common among Ashkenazi Jews. One in eight Ashkenazi Jews is thought to be a carrier of factor XI deficiency. In one study, 1 in 190 Ashkenazi Jews has a severe bleeding problem related to factor XI deficiency, while a different study found a much lower rate of severe symptoms, 1 in 450. Among non-Jews in the United States, only 1 in 1,000,000 have factor XI deficiency, making it very rare.
The disease is also common among families in northwest England, where 1 in 10,000 people has the disease. Other groups at greater risk for carrying mutations that cause factor XI deficiency are Iraqi Jews, Sephardic Jews, and people of Arab background living in Israel.
In the United States, factor XI deficiency is treated with infusions of fresh frozen blood plasma. This blood plasma contains normal quantities of factor XI, thus temporarily enhancing the body’s ability to clot. However, significant amounts of plasma may be required to achieve the desired clotting effect due to the low concentration of factor XI in plasma.
In Europe, there are several commercially available concentrated doses of factor XI. One is manufactured in the United Kingdom, the other in France.
In the case of bleeding in the mouth, nose, intestines, or uterus, there are several medications which may be helpful, though they are not effective for major internal bleeding and can cause clotting throughout the body.
Factor XI deficiency is not known to affect lifespan. In people who do not realize they have the disease, life-threatening bleeding is possible following surgery or injury.
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