BackgroundAcquired hemophilia A (AHA) is a rare disease characterized by a prolonged activated partial thromboplastin time (aPTT) and the production of coagulation factor VIII inhibitors. We encountered two cases of AHA in the perioperative period of pancreatoduodenectomy (PD).Case presentationCase 1: A 76-year-old woman with intraductal papillary mucinous carcinoma developed acute cholecystitis 5 days before PD. Despite immediate improvement in her acute cholecystitis with biliary drainage and antibiotics, her aPTT level was prolonged (55.9 s). PD was performed as scheduled. On postoperative day (POD) 2, she developed intra-abdominal hemorrhaging that required reoperation. However, intra-abdominal bleeding and concomitant anemia persisted after reoperation. On POD 13, she was diagnosed with AHA based on the detection of an inhibitor of coagulation factor VIII. Despite hemostatic and immunosuppressive treatment, including massive blood transfusion, her general condition gradually worsened due to continuous bleeding and secondary infections. She ultimately died of multiple organ failure on POD 71.Case 2: An 82-year-old man received PD for distal cholangiocarcinoma. On POD 3, a small amount of blood via abdominal drainage was observed. On POD 4, his aPTT level was prolonged (61.5 s). On POD 8, subcutaneous hemorrhaging of the median wound was observed, and corticosteroids were administered under suspicion of AHA on POD 9. On POD 15, an inhibitor of FVIII was detected, and he was diagnosed with AHA. On POD 17, the aPTT level had normalized, and an inhibitor of FVIII was undetectable. On POD 41, he was discharged without any serious hemorrhagic events.ConclusionsAHA may be more frequent than previously reported. When unexplained prolonged aPTT or bleeding symptoms are observed, it is important to keep AHA in mind during the perioperative period of invasive surgery.