Antiphospholipid syndrome (APS) is the most common cause of acquired thrombophilia due to the presence of persistent antiphospholipid antibodies that promote a hypercoagulable state by interfering with coagulation pathways and endothelial function. These antibodies increase the risk of both venous and arterial thrombosis, leading to significant clinical complications such as deep vein thrombosis, stroke, and pregnancy morbidity. APS can occur as a primary disorder or secondary to autoimmune diseases like systemic lupus erythematosus. Unlike inherited thrombophilias, APS is characterized by laboratory detection of lupus anticoagulant, anticardiolipin, or anti-β2 glycoprotein I antibodies. Recognition and management of APS are crucial in patients with unexplained thrombotic events. Key surgical consideration: Patients with APS undergoing surgery have a high risk of perioperative thrombosis and require tailored anticoagulation protocols.

Reference: Harrison's Principles of Internal Medicine, 20th Edition.