A Clinical and Experimental Study of Acquired Inhibitors to Factor VIII

Factor VIII inhibitors which developed in four patients with hemophilia A are described. These inhibitors are apparently specific for Factor VIII and are capable of inducing a transient hemophilic state when injected into dogs. The genesis, properties, and mode of action of these inhibitors can be explained on an immunologic basis and it seems most likely that they represent an antibody to Factor VIII. One hemophilia A patient, with retroperitoneal hematoma and a potent Factor VIII inhibitor, was successfully treated by an exchange transfusion followed by administration of purified porcine Factor VIII.