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Factor XII


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Factor XII

Factor XII


Factor XII (FXII) deficiency, also called Hageman factor deficiency, was first identified in 1955 in John Hageman. Its incidence is estimated at one per one million. FXII deficiency is inherited in an autosomal recessive fashion, meaning both parents must carry the gene to pass it on to their children; it affects men and women equally. It is more common in Asians than other ethnic groups.

FXII interacts with the activation of FXI to FXIa to generate thrombin, a protein that converts fibrinogen to fibrin, which traps platelets and helps hold a clot in place.


Some people with FXII deficiency experience poor wound healing. However, most do not display bleeding manifestations, even after major surgery.


Since bleeding time is usually normal, diagnosis is made by a prolonged activated partial thromboplastin time (aPTT) test. Although this scenario can be seen in patients with other contat factor deficiencies (prekallikrein, high-molecular weight kininogen), a specific assay for factor XII will help confirm the diagnosis.


No treatment is required for factor XII-deficient patients.