Heterotaxy syndrome: a rare risk factor for a pulmonary embolism in a young person.

Heterotaxy syndrome, or situs ambiguus, is a rare congenital condition characterized by abnormal left-right positioning of thoracoabdominal organs. It often includes splenic anomalies such as polysplenia and vascular malformations like interruption of the inferior vena cava (IVC) with azygos continuation. These anatomical variants can impair venous return, increasing the risk of venous thromboembolism, particularly in young patients. We present the case of an 18-year-old woman with obesity and long-term estrogen-containing oral contraceptive use who presented with acute bilateral pulmonary emboli. Initial imaging noted polysplenia, but the diagnosis of heterotaxy syndrome with IVC interruption and azygos continuation was not made until 5 months later during evaluation for recurrent chest pain. Hypercoagulable workup was negative, and anticoagulation was continued due to ongoing thrombotic risk. This case highlights heterotaxy syndrome as an underrecognized contributor to venous thromboembolism in young individuals and underscores the importance of considering anatomical risk factors in cases of unprovoked thromboembolism.