Coagulation factor XIII (F13) circulates in blood as a heterotetramer composed of an A subunit dimer and a B subunit dimer. It is activated by thrombin and crosslinks fibrin monomers. Congenital F13 deficiency demonstrates a lifelong bleeding tendency, abnormal wound healing, and recurrent miscarriages, and it first manifests as umbilical bleeding after birth. In contrast, secondary F13 deficiencies due to its overconsumption and/or hypobiosynthesis by disseminated intravascular coagulation, major surgery, liver diseases, and other disorders are rather common but rarely complicated with bleeding symptoms. Recently, consultations with physicians who have patients with hemorrhagic-acquired F13 deficiency with anti-F13 inhibitors (acquired hemorrhaphilia 13) have indicated an increase in this disease in Japan. We performed a nationwide survey, supported by the Japanese Ministry of Health, Welfare and Labor and confirmed 21 Japanese cases of this disease with anti-F13 inhibitors. Because neither prolonged clotting times nor reduced platelet counts are observed in patients with this disease, many more cases may have been overlooked. Physicians must be mindful of acquired hemorrhaphilia 13 when seeing such patients and should measure F13 activity. Products containing F13 are effective for hemostasis generally, and immunosuppressive therapy must be started immediately to eradicate anti-F13 antibodies.
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