subunit of plasma factor XIII; a novel form of acquired factor XIII deficiency Severe bleeding complications caused by an autoantibody against the B

Abstract Acquired factor XIII (FXIII) deficiency due to autoantibody against FXIII is a very rare severe hemorrhagic diathesis. Antibodies directed against the A subunit of FXIII, which interfere with different functions of FXIII, have been described. Here, for the first time, we report an autoantibody against the B subunit of FXIII (FXIII-B) that caused life-threatening bleeding in a patient with systemic lupus erythematosus. FXIII activity, FXIII-A 2 B 2 complex and individual FXIII subunits were undetectable in the plasma, while platelet FXIII activity and antigen were normal. Neither FXIII activation nor its activity was inhibited by the antibody, which bound to structural epitope(s) on both free and complexed FXIII-B. The autoantibody highly accelerated the elimination of FXIII from the circulation. FXIII supplementation combined with immunosuppressive therapy, plasmapheresis, immunglobulin and anti-CD20 treatment resulted in the patient’s recovery. FXIII levels returned to around 20% at discharge and after gradual increase it stabilized above 50%. Keywords: coagulation, acquired coagulation disorders, factor XIII, factor XIII B subunit, autoantibody against factor XIIIFrom bloodjournal.hematologylibrary.org by guest on June 6, 2013. For personal use only.