Acute Groin Pain Revealing Acquired Hemophilia A: A Case Report of Spontaneous Iliopsoas Hematoma.

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by the development of autoantibodies against coagulation factor VIII, resulting in potentially life-threatening hemorrhage. Because affected patients typically lack a personal or family history of bleeding disorders and often present with nonspecific symptoms, diagnosis may be delayed. We report the case of a previously healthy 60-year-old woman who presented with acute progressive left groin pain caused by a spontaneous iliopsoas hematoma with active arterial bleeding. Initial laboratory evaluation revealed an isolated prolonged activated partial thromboplastin time (aPTT), while further coagulation studies demonstrated a factor VIII activity of 6% and a factor VIII inhibitor titer of 6.7 Bethesda Units, confirming the diagnosis of AHA. The patient was successfully treated with recombinant activated factor VII, high-dose corticosteroids, and emicizumab, resulting in rapid clinical improvement and initial remission. However, disease recurrence occurred during follow-up, requiring escalation of immunosuppressive therapy. This case highlights the diagnostic challenges of AHA when presenting with atypical symptoms such as acute groin pain due to spontaneous iliopsoas hematoma. It further emphasizes that even a moderately prolonged isolated aPTT in a patient with spontaneous bleeding should prompt immediate evaluation for an acquired coagulation disorder. Early recognition and prompt multidisciplinary management are essential to prevent potentially life-threatening hemorrhagic complications.