Abstract Number: Esoc2026a946 Concomitant Ischemic Stroke and Deep Vein Thrombosis in a Patient With Severe Antithrombin Iii Deficiency: A Case Report

Abstract Background and aims Antithrombin III (ATIII) deficiency is a rare hereditary thrombophilia primarily associated with venous thromboembolism. The synchronous occurrence of arterial ischemic stroke and deep vein thrombosis (DVT) represents a highly atypical clinical phenotype, posing significant diagnostic challenges in young adults. This report delineates a unique case of concomitant arterial and venous thrombosis secondary to profound ATIII deficiency. Methods A 46-year-old male presented with acute-onset left hemiparesis and apathy. His medical history was notable for recurrent DVT and prior cerebral venous sinus thrombosis. A comprehensive diagnostic work-up was executed, comprising multimodal brain MRI, Doppler ultrasonography, echocardiography, and a directed serological evaluation for hereditary and acquired thrombophilic states. Results Magnetic resonance imaging (MRI) revealed an acute infarction in the right anterior cerebral artery (ACA) territory. Subsequent Doppler ultrasound revealed extensive left femoral and popliteal DVT. A comprehensive stroke work-up, including transthoracic echocardiography, carotid duplex, and screening for patent foramen ovale (PFO), was unremarkable. Specialized thrombophilia testing identified a profound reduction in ATIII activity (38%; reference: 83–128%), while Protein C, Protein S, and Factor V Leiden levels were within normal limits. The patient was initiated on rivaroxaban and achieved significant functional recovery through multidisciplinary rehabilitation. Conclusions Severe ATIII deficiency may manifest through concurrent arterial and venous thrombotic events. A high index of clinical suspicion for hereditary thrombophilia is warranted in young patients presenting with cryptogenic stroke, particularly those with a personal or familial history of thromboembolism. Precise diagnosis is imperative for optimizing long-term secondary prevention and guiding familial screening protocols. Conflict of interest Huong Nguyen: nothing to disclose