COL3A1 and thoracic aortic aneurysm: <b>Background/Objectives:</b> Thoracic aortic aneurysms have long been associated with germline mutations such as <i>FBN1</i>, <i>TGFBR2</i>, and <i>COL3A1</i>, which predispose to Marfan, Loeys-Dietz, and Ehlers-Danlos syndromes, respectively.