Increased MMP9, an elastolytic protease with both pro- and anti-inflammatory effects, has been implicated in several disorders including cardiovascular diseases (atherosclerosis, aortic aneurysm, myocardial infarction, and vascular inflammation (51)) and KD where it may play a role in development of coronary artery aneurysms (52–54). This evidence concerns the gene MMP9 and coronary aneurysm.