A Rare Case of Antiphospholipid Syndrome With Concomitant Antithrombin III Deficiency: A Case Report.

Antithrombin (AT) deficiency and antiphospholipid syndrome (APS) are distinct but potentially overlapping disorders with significant implications for thrombosis. We present a case of a 28-year-old male with hereditary AT deficiency who subsequently developed primary APS. Despite the challenges of overlapping symptoms and anticoagulation therapy, a careful diagnostic approach revealed the coexistence of these rare conditions. The patient was successfully managed with long-term anticoagulation, hydroxychloroquine, and other supportive measures. This case underscores the importance of comprehensive laboratory testing, especially when managing patients with pre-existing anticoagulation needs.