True aneurysms of the pulmonary artery are rare, and are most often due to pulmonary hypertension arising from congenital heart defects. We report the case of a 40-year-old man with an uncorrected patent ductus arteriosus who presented with pulmonary infarction and pneumonia, and subsequently died of cardiac arrest. Autopsy revealed a large pulmonary artery aneurysm, in situ pulmonary artery thrombosis complicated by pulmonary infarction, pulmonary artery dissection, and cardiac tamponade. Although each of these complications is rare in and of itself, this case demonstrates the entire spectrum of complications from a single uncorrected congenital cardiac anomaly.