Factor XI Deficiency

Factor XI (FXI) is involved in thrombin generation by activating Factor IX (FIX) in the intrinsic coagulation pathway. FXI deficiency, also known as hemophilia C, is an autosomal recessive disorder associated with a variable bleeding phenotype. It is most common in persons of Ashkenazi Jewish ancestry but can also be found in other ethnic groups. Clinical symptoms correlate poorly with FXI activity, and abnormal bleeding usually happens after trauma or surgical challenge. The laboratory diagnosis requires an FXI activity assay because partial thromboplastin time can be normal in persons with mild FXI deficiency. Plasma, antifibrinolytics, and FXI concentrates are currently used in management and prevention of bleeding.