Introduction

Acquired factor VIII (F VIII) deficiency, alternatively known as acquired hemophilia A (AHA), is a rare and potentially life-threatening bleeding disorder caused by the development of autoantibodies that are directed against F VIII [1]. F VIII plays an important role in the coagulation cascade as it facilitates the activation of factor X, necessary for blood clotting. AHA typically arises later in adulthood, with an estimated incidence of one case per million annually [2]. A study showed that patients with AHA had a one-year survival rate of approximately 68% [3]. Diagnosis of AHA requires a high index of suspicion, especially in patients with isolated prolonged aPTT not corrected by mixing studies. The F VIII activity level must be low or absent, and the Bethesda assay would measure the strength of inhibition [3].

AHA can be caused by certain medications, including beta-lactam antibiotics, non-steroidal anti-inflammatory drugs, and heparin [4]. AHA may also occur in the postpartum setting or in association with autoimmune disorders or malignancies. However, in up to 79% of cases, no clear etiology is found. Clinically, patients commonly present with soft tissue hematomas, mucosal bleeding, or life-threatening hemorrhages in the absence of a bleeding history [2]. Antiphospholipid antibodies (aPL) bind to phospholipid-binding plasma proteins on cellular surfaces, triggering prothrombotic pathways that promote a hypercoagulable state. Lupus anticoagulant (LAC), a subtype of aPL, is paradoxically associated with thrombosis despite prolonging phospholipid-dependent coagulation assays, including the activated partial thromboplastin time (aPTT) [5]. Meanwhile, antiphospholipid antibodies (aPL) refer to a group of autoantibodies that affect phospholipid-dependent coagulation assays, leading to prolonged clotting times in vitro. These antibodies most commonly target phospholipid-binding plasma proteins such as β2-glycoprotein I and anticardiolipin antibodies [5]. This paradox arises because LAC enhances thrombin generation in vivo by concentrating prothrombin on phospholipid surfaces. The presence of aPL is a major risk factor for the development of antiphospholipid syndrome (APS), which is characterized by both arterial and venous thromboembolic events [6].

The co-existence of both AHA and LAC is exceedingly rare, with fewer than 20 documented cases. We report a case of a patient with no prior bleeding history who presented with a soft tissue hematoma, severe acquired F VIII deficiency, and positive lupus anticoagulant in the absence of a clear etiology.