Rare cause of dyspnea: yin-yang thoracic aortic aneurysm.

Aortic aneurysmal diseases, mostly found incidentally, have high mortality and morbidity. Complications mostly are associated with and accelerated in the presence of systemic hypertension, aortic valve disease, or aortic atherosclerosis. Presenting signs and symptoms can be nonspecific and need immediate and accurate recognition. We present a case of incidental finding of a large descending aortic aneurysm with "yin-yang" sign and discuss the importance of differentiating pseudoaneurysm versus intramural thrombus.