A 56-year-old woman presented at our emergency department with nausea and acute chest pain that radiated to her interscapular region and left leg. She had experienced no syncope, vomiting, or shortness of breath. Her medical history included smoking and a myocardial infarction 16 years earlier. Her family history included coronary artery disease and an aortic aneurysm. On presentation, her physical indings were unremarkable except for hypertension (160/110 mmHg). She was admitted to the critical care unit and given intravenous nitroprusside and metoprolol for blood-pressure control. Because aortic dissection was suspected, she underwent contrast-enhanced computed tomography (CT), which revealed dilation of the sinuses of Valsalva (maximum diameter, 5.6 cm) and effacement of the sinotubular junction (Fig. 1). A Stanford type B aortic dissection was also present; the intimal flap began just distal to the origin of the left subclavian artery, involved the entire descending thoracoabdominal aorta, and extended distally into both common iliac arteries (Fig. 2). At the L4, L5, S1, and S2 levels, the dural sac was enlarged (maximum diameter, 2.7 cm; dural sac ratio >0.98) (Fig. 3). On the basis of these indings alone, Marfan syndrome was diagnosed. An aortic stent was placed at the origin of the dissection, and the patient recovered uneventfully. Fig. 1 Contrast-enhanced computed tomographic image at the level of the left atrium shows aneu-rysmal dilation of the aortic root (maximum diameter, 5.6 cm) (arrow), and dissection of the descending thoracic aorta (arrowhead denotes the intimal flap). ... Fig. 2 Computed tomographic (CT) images of aortic dissection. A) Axial CT image at the level of the aortic arch shows the origin of the dissection flap distal to the origin of the left subclavian artery (arrow). B) Image at the level of the kidneys reveals ... Fig. 3 Computed tomographic (CT) images of dural ectasia. A) Axial CT image obtained at the level of the mid sacrum reveals ectasia of the dural sac at the S1 and S2 levels (arrowheads). B) Multiplanar reformation in the sagittal view shows enlargement ...