Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion

Background: Major aortopulmonary collateral arteries (MAPCAs) are anomalous systemic-to-pulmonary vessels typically associated with complex congenital heart disease. Isolated MAPCAs in adults without structural cardiac abnormalities are exceedingly rare, and aneurysmal degeneration is even more uncommon. Case presentation: We report a 48-year-old man presenting with acute non-exertional chest pain. Computed tomography angiography (CTA) demonstrated a 2.6-cm saccular aneurysm arising from an isolated MAPCA originating from the proximal descending thoracic aorta and supplying the left lower lobe pulmonary artery. CTA delineated the vascular anatomy and excluded associated congenital cardiac abnormalities. Digital subtraction angiography confirmed a single systemic-to-pulmonary arterial communication. The patient underwent thoracic endovascular aortic repair with adjunctive coil embolization, resulting in complete aneurysm exclusion and symptom resolution. Conclusions: This case highlights the importance of recognizing isolated aneurysmal MAPCAs in adults, the value of CTA in diagnosis and procedural planning, and the effectiveness of endovascular therapy in preventing potentially life-threatening complications.