[Examination of the inhibitor to factor VIII in non-haemophilic patient]

We examined an inhibitor to factor VIII in non-haemophilic patient who had been developed widely spread ecchymosis and intramuscular bleeding. He had no previous personal or family history of abnormal bleeding tendency. His laboratory data was all normal except examination for blood coagulation. Coagulation studies showed prolonged activated partial thromboplastin time (48 sec) and decreased factor VIII activity (8%). The activity of the inhibitor to factor VIII was demonstrated to be 4.0 Bethesda unit. By the studies of dilution and time response curve, this inhibitor was found to inhibit up to 90% of factor VIII activity but not 100%. This inhibitor was shown to be IgG by protein-A affinity chromatography. In addition, bleeding time was prolonged in the patient. The value of von Willebrand factor antigen was 200%, but that of Ristocetin cofactor was 93%. Since the gel filtration analysis indicated that this inhibitor also suppressed Ristocetin cofactor activity, the relatively low value of Ristocetin cofactor might occur through the action of the inhibitor. These data suggest that patient's inhibitor react to factor VIII high molecular subunit.