Autoimmune acquired factor XIII (F13) deficiency or autoimmune hemorrhaphilia resulted from the generation of anti-F13 antibodies (AHFXIII) is a rare but severe life-threatening bleeding disorder. In contrast, non-autoimmune hemorrhagic acquired F13 deficiency (HAF13D) is a less severe bleeding disease secondary to various disease conditions. AHFXIII must be distinguished from HAF13D since AHFXIII requires immunosuppressive therapy to eradicate autoantibodies in addition to F13 replacement therapy to arrest bleeding. Patients with acquired F13 deficiency, in particular those with AHFXIII, are on the increase, at least in Japan.
