Factor V inhibitor with double cancer

A 84-year-old man was admitted with palpitation, edema of legs and anemia during a long course of diabetes mellitus, prostatic hypertrophy and prostatic cancer. He revealed purpura on the hands and massive microhematuria. He had received antibiotic therapy for a urinary tract infection for a period of time, but he had no history of hemorrhagic tendency or blood transfusion. Coagulation studies showed the prolongation of whole blood clotting time and PT (prothrombin time). Activity of factor V was 14% of that normal control plasma. The titer of factor V inhibitor was 4.9 Bethesda units/ml. The inhibitor of the patient was supposed to belong to IgA and IgG judging from inhibitor neutralization test. PT was improved after discontinuance of administration of antibiotics and administration of azathioprine. Moreover, even after administration of prednisolone with antibiotics, PT and activity of factor V recovered to normal range. He died from respiratory failure. Autopsy revealed double cancer of prostate and descending colon. The appearance of factor V inhibitor was likely caused by antibiotics, double cancer, and age-related immune disorders.