Acquired Haemophilia A Associated With Suspected Chronic Neutrophilic Leukaemia Presenting As Fatal Retroperitoneal Haemorrhage in an Elderly Patient.

Acquired haemophilia A (AHA) is a rare but potentially life-threatening bleeding disorder caused by autoantibodies against coagulation factor VIII. It often presents with spontaneous bleeding and prolonged activated partial thromboplastin time (aPTT) and is commonly associated with autoimmune disorders, malignancy, or idiopathic causes. Chronic neutrophilic leukaemia (CNL) is a rare myeloproliferative neoplasm that has occasionally been linked with paraneoplastic phenomena, including AHA. An elderly patient presented following a fall with normal imaging but was noted to have a markedly prolonged aPTT (78-104 seconds), normal prothrombin time (PT), and an isolated severe factor VIII deficiency (<0.01 IU/mL). A Bethesda assay confirmed high-titer factor VIII inhibitors, with a measured level of 9 Bethesda units (BU). No underlying autoimmune disease or malignancy was identified initially; however, persistent neutrophilia over several years raised suspicion of undiagnosed CNL. The patient subsequently developed retroperitoneal haemorrhage with a significant haemoglobin drop, requiring transfusion. Later, the patient suffered an ST-elevation myocardial infarction (STEMI) and, after a multidisciplinary discussion, was transitioned to palliative care. Sadly, the patient passed away eight days post-admission. This case highlights the diagnostic and therapeutic challenges of AHA, particularly when associated with occult or undiagnosed haematological malignancies like CNL. Early recognition and immunosuppressive therapy are crucial to improving outcomes.