Internal thoracic artery aneurysm coincidental with protein S deficiency: a case report.

BACKGROUND: Internal thoracic artery aneurysms are exceptionally rare and carry a risk of fatal rupture. Although pseudoaneurysms are commonly associated with trauma or surgical interventions, the development of true aneurysms promoted by thrombotic disorders has not been previously reported. CASE PRESENTATION: A 61-year-old man undergoing hemodialysis for end-stage renal disease due to untreated nephrotic syndrome presented with hemoptysis. He had a medical history of deep vein thrombosis and was taking warfarin. Imaging studies revealed pulmonary embolism, systemic collateral circulation, a 21-mm aneurysm of the left internal thoracic artery, and a 9-mm aneurysm of the left bronchial artery. Laboratory investigations confirmed acquired protein S deficiency, likely caused by nephrotic syndrome. The internal thoracic artery aneurysm, due to concern for rupture, was successfully treated with percutaneous catheter arterial embolization, while the left bronchial arterial aneurysm was managed conservatively without intervention because of its small size. The patient recovered without complications and remained stable during a 5-year follow-up. CONCLUSIONS: This case highlights a rare presentation of internal thoracic artery aneurysm coinciding with acquired protein S deficiency and nephrotic syndrome. Although a direct causal relationship between protein S deficiency and aneurysm formation is difficult to establish, the co-occurrence of these conditions underscores the importance of careful vascular assessment in similar patients.