A case of autoimmune factor XIII deficiency due to clearance-accelerating and inhibitory anti-FXIII autoantibodies.

A 63-year-old man, previously diagnosed with multiple autoimmune diseases, developed life-threatening bleeding after gastrectomy for stomach cancer. He survived due to treatment with factor XIII (FXIII) concentrates immediately after his FXIII antigen (Ag) level was reported to be < 5% of normal. Detailed examination by the Japanese Collaborative Research Group on autoimmune coagulation factor deficiencies revealed the presence of anti-FXIII-A and anti-FXIII-B subunit autoantibodies on immunoblot analyses, and thus autoimmune FXIII deficiency (AiF13D) was diagnosed based on the Japanese and international diagnostic criteria. Antibody eradication therapy with prednisolone was initiated and cyclophosphamide was added later. While FXIII:Ag levels remained at 40-50% of normal, bleeding did not recur even after stomach polypectomy. Experimental studies on patient specimens collected at the initial bleeding and later asymptomatic stages demonstrated the co-existence of clearance-accelerating and inhibitory anti-FXIII autoantibodies. The former type was predominant in both the bleeding and asymptomatic stages, whereas the latter became distinct in the asymptomatic stage. This is the first AiF13D patient to demonstrate such a change in anti-FXIII autoantibody type during the clinical course. This report discusses the relationship between autoantibody type and bleeding phenotype in detail, but future large studies are needed to confirm these observations.