Abstract
A 74 year-old male with rheumatoid arthritis and double cancer (laryngeal cancer and early stomach cancer) showed prolongation of prothrombin time and activated partial thromboplastin time by preoperative coagulation screening tests and was subsequently found to be suffering from an inhibitor against factor V. With specific antiserum and neutralization tests, the inhibitor was characterized as an IgG (κ) antibody. Factor V inhibitor disappeared following radiotherapy, and no inhibitor has been detected for 2 years. This inhibitor was able to inactivate Factor V of some animals such as horse, sheep, goat, rabbit and dog. Although the inhibitor inactivated Factor V either in human plasma or in animal plasmas, no clinical bleeding tendency was observed.
