Factor XI deficiency is a rare inherited bleeding disorder that occurs when an individual has too little of a protein called factor XI. Factor XI is a clotting factor that plays a key role in the clotting, or coagulation, cascade that is triggered when a blood vessel is damaged. Factor XI may also be called hemophilia C or Rosenthal syndrome. Hemophilia refers to an inherited clotting disorder. There are three types of hemophilia: A, B, and C. Dr. Rosenthal first described Factor XI deficiency in 1953 and originally called it "plasma thromboplastin antecedent deficiency."
Clotting or coagulation disorders occur when the blood does not form clots properly. Blood clots are clumps of different types of blood cells and proteins called clotting factors that stop bleeding after an injury. The process of blood clotting is called coagulation or hemostasis.
When a blood vessel breaks due to an injury or surgical incision, it narrows to slow blood flow so that clotting can begin. At the same time, the blood that has leaked outside of the injured blood vessel presses against the vessel to help prevent further blood loss. Blood cells called platelets are activated to move toward the site of injury. Once platelets reach the site of injury, a series of reactions started by enzymes called coagulation factors lead to the activation of a protein called thrombin. Factor XI is one of the coagulation factors. These factors convert a blood clotting factor, fibrinogen, into long strands that form a net around the platelets and blood cells to help trap more platelets to form a blood clot.
The blood clot, called a thrombus, is a temporary plug to control bleeding. Once the platelets are clumped together, they become activated and stick together. Sometimes blood clots are visible and appear as bruises under the skin or scabs on the skin. Once the blood vessel is healed, other blood factors are released to destroy the clot by dissolving it into the blood.
People with Factor XI deficiency are unable to properly form clots and may experience prolonged bleeding in response to severe injuries. However, they do not experience spontaneous bleeding in the absence of injury or other trauma. Patients may experience excessive and potentially fatal bleeding after undergoing surgical or dental procedures. The risk of hemorrhaging, or uncontrolled bleeding, may vary throughout an affected person's life.
Factor XI deficiency is the fourth most common coagulation disorder after von Willebrand's disease and hemophilia A and B. Bleeding episodes associated with Factor XI deficiency are milder and occur less frequently than bleeding episodes in these other bleeding disorders. Although the symptoms of Factor XI deficiency can occur at any age, many people with this condition do not even know they have it. Factor XI deficiency is often first detected during the routine blood testing that happens before a surgical procedure.
Treatment of Factor XI deficiency is usually necessary only in the case of a surgery or a severe injury. Treatment involves replacement of factor XI using fresh frozen plasma, which contains factor XI and other clotting factors.
Factor XI deficiency is caused by a genetic defect, or mutation, in the F11 gene that codes for the factor XI protein. The disease is caused by different mutations in different people. More than 80 different mutations have been found that result in Factor XI deficiency and some are found in genes other than the F11 gene. Men and women are affected in equal numbers. This disorder affects approximately one out of 100,000 people worldwide.
Anemia, bleeding, blood disorder, clotting, coagulation, factor XI, FXI deficiency, hemophilia, hemophilia C, hemorrhage, menorrhagia, plasma thromboplastin antecedent deficiency, PTA, Rosenthal's syndrome, Rosenthal syndrome, thrombosis.