Here we present a rare case of pulmonary arterial thrombosis associated with a ductus arteriosus aneurysm that caused severe pulmonary stenosis. A 5-day-old newborn was admitted to our hospital for the evaluation of an intracardiac mass-like lesion found after the detection of a cardiac murmur. Echocardiography and heart computed tomography revealed a mass-like lesion measuring 8. https://www.kingarte.com/product-category/glass-frostersglass-chillers/