Factor XI Deficiency
(Also known as Hemophilia C, Plasma Thromboplastin Antecedent (PTA) Deficiency, Rosenthal Syndrome.)
Factor XI Deficiency was only first recognized in 1953. The incidence of Factor XI Deficiency is estimated at 1 in 100,000. It is inherited in an autosomal dominant fashion, which means it affects men and women equally. In Israel, Factor XI Deficiency has been estimated to be around 8% among individuals of Ashkenazi Jewish descent.
Factor XI is another part of the cascade of clotting factors that form the chain leading to a protective clot. Some people with Factor XI deficiency may have milder symptoms that those of hemophilia, but there can be quite a bit of variability with this deficiency. Symptoms of Factor XI Deficiency include:
- Blood in the urine
- Woman may experience menorrhagia and prolonged bleeding after childbirth
- Joint bleeds are uncommon
Individuals are not likely to bleed spontaneously, and hemorrhage normally occurs after trauma or surgery. However, certain procedures carry an increased risk of bleeding such as:
- dental extractions
- surgery in the urinary and genital tracts
- nasal surgery
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 extremely useful in ruling out combined deficiencies.
In the United States, there are no factor XI concentrates available and fresh-frozen plasma is normally used for treatment. Since Factor XI is not concentrated in fresh frozen plasma, considerable amounts of plasma may be required to maintain the factor level. In the case of mouth bleeds, antifibrinolytic products such as Amicar can be helpful.
Currently there are two factor XI concentrates produced in Europe. One is manufactured through Bioproducts Laboratories (BPL) in the UK. The other product is produced in France through LFB and only for limited patient use.