Factor XI Deficiency

The incidence of factor XI deficiency is estimated at 1 in 100,000. It is inherited in an autosomal dominant fashion, which means it is equally likely to affect men and women. It occurs with greater frequency in people of Ashkenazi Jewish descent, likely because intermarriage among this group has been more common.

Factor XI is another clotting factor that helps the body form a protective blood clot. Most people with factor XI deficiency have milder symptoms than those seen with hemophilia, but this can vary. Individuals with factor XI deficiency are not likely to have spontaneous bleeding, and hemorrhage typically occurs after trauma or surgery. Certain procedures, such as dental extractions, tonsillectomies, urinary and genital tract surgery and nasal surgery, carry an increased risk of bleeding. Joint bleeds, however, are uncommon. However, patients are more susceptible to bruising, nosebleeds, and blood in the urine. Woman may experience menorrhagia and prolonged bleeding after childbirth.

Diagnosis is made through bleeding time test, platelet function tests and prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests. A specific factor XI assay is useful in ruling out combined deficiencies.

Treatment

No factor XI concentrates are currently available in the United States, and fresh-frozen plasma (FFP) is typically used for treatment. Since factor XI is not concentrated in FFP, substantial amounts of plasma may be required to maintain the factor level. Antifibrinolytic products can be helpful for mouth bleeds.

Two factor XI concentrates are produced in Europe. One is manufactured through Bioproducts Laboratories (BPL) in the United Kingdom. The other product is manufactured in France through LFB, but it is only for limited patient use.