What is the most likely diagnosis for a young woman with left lower extremity swelling and a history of deep vein thrombosis?

The diagnosis that best fits a young woman with left lower extremity swelling and a history of deep vein thrombosis is antiphospholipid antibody syndrome. This condition is characterized by the presence of antiphospholipid antibodies, which can lead to recurrent venous and arterial thrombosis. In this scenario, the young woman’s history of deep vein thrombosis suggests a propensity for clot formation, and the current swelling of her left lower extremity further indicates a potentially new or recurrent thrombotic event.

Antiphospholipid antibody syndrome commonly presents in young women, as they are at an increased risk for thrombotic events due to various factors, including hormonal influences from pregnancy or contraceptive use. The involvement of the left lower extremity swelling implies that there may be a venous thromboembolism occurring.

Other choices, while they can contribute to thrombotic events, do not align as closely with the provided clinical scenario. For example, heterozygous factor V Leiden could also cause thrombosis, but it does not specifically address the recurrent nature seen in antiphospholipid antibody syndrome. Similarly, atrial myxoma is a cardiac tumor that might lead to embolic events but is less likely to present solely as