We report the case of a 86-year-old man admitted in a local hospital with spontaneous haematoma, an isolated prolonged activated partial prothrombin time (114/32 seconds; ratio = 3.6), an anemia and a normal platelet count. Two diagnosis were suspected: a coagulation factor defect, or the presence of a lupus anticoagulant or of anti-factor antibodies. An acquired haemophilia A was confirmed with a factor VIII activity level < 1 U/dL associated with the presence of an anti-factor VIII inhibitor. The factor VIII inhibitor titer reached 195 Bethesda U/mL. A prostatic adenocarcinoma was suspected: a 5 cm prostatic tumour was found and the PSA level was 113 ng/mL. The patient was treated with recombinant factor VIIa: Novoseven (90 microg/kg). None immunosuppressive agents were prescribed in this elderly patient. The patient's disease was identified as a spontaneously acquired haemophilia A associated with prostatic adenocarcinoma.