What Is Factor XI Deficiency? 

Factor XI deficiency (plasma thromboplastin antecedent) is an inherited bleeding disorder caused by a defect or lack of a protein in the blood (factor XI) that helps blood clot. The disorder is also known as hemophilia C. It differs from hemophilia A or B in that there is no bleeding into joints and muscles. Factor XI deficiency is the most common of the rare bleeding disorders, estimated at one in 100,000 people, and is the second most common bleeding disorder affecting women, after von Willebrand disease.

Some people have inherited factor XI deficiency when only one parent has carried the gene and can bleed excessively. Factor XI deficiency is reported in all races but it is most common among Ashkenazi Jews, that is, Jews of Eastern European ancestry. Eight percent of that population carries the defective gene. The gene is found on chromosome 4.

Symptoms

Most people with factor XI deficiency experience little or no bleeding. Symptoms vary widely, even among family members. This makes it more difficult to diagnose.

People with factor XI deficiency may experience:

• heavy or prolonged bleeding during menstrual periods (menorrhagia)
• abnormal bleeding after tooth extraction, surgery, or trauma (injury)

Diagnosis

Factor XI deficiency is diagnosed by a variety of blood tests to see if there is a bleeding disorder and, if so, to determine which one it is.

Treatment

Factor XI deficiency is treated with:

• antifibrinolytic drugs( drugs that can help stop the normal breakdown of blood clots and help speed recovery from a bleed)
• factor XI concentrates
• factor VIIa concentrates
• fresh frozen plasma (FFP)

Content reviewed by Dr. Paula Bolton-Maggs
Consultant Haemotologist
Manchester Haemophilia Comprehensive Care
Manchester Royal Infirmary
Manchester, UK.

Updated December 2007