While gain-of-function variants in <i>MYH11</i> are associated with thoracic aortic aneurysms and dissections, loss-of-function variants are linked to autosomal recessive Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome (MMIHS). This evidence concerns the gene MYH11 and thoracic aortic aneurysm.