Penetrating Aortic Ulcer (PAU)is an advanced focal form atherosclerosis, most often encountered in the aorta. It starts as a small plaque in the inner-most layer of the aorta called the intima, but the inflammatory process ulcerates and penetrates through this layer into the media. While PAU is considered a distinct entity, many think this is a precursor lesion to dissection or aneurysm. Along with Intramural Hematoma, Aneurysm and Dissection, PAU is recognized as one of several Acute Aortic Syndromes—a spectrum of related conditions correlated to potential aortic rupture. They thus have a high potential morbidity and mortality, and should at least be followed closely.