Objectives: Marfan Syndrome (MFS) is a connective tissue disorder commonly associated with Thoracic Aortic Aneurysms (TAAs). TAAs occur because of abnormal remodeling of the aortic extracellular matrix (ECM). The balance between matrix metalloproteinases (MMPs) and the Tissue Inhibitors of MMPs (TIMPs), regulates these processes. The extracellular MMP inducer (EMMPRIN), is a widely expressed glycoprotein capable of stimulating the production of various MMPs, suggesting a direct role in driving pathology. The Membrane Type-1 MMP (MT1-MMP) can cause proteolytic shedding of EMMPRIN. Therefore, we investigated this relationship in MFS TAA tissue and plasma and tested the hypothesis that a unique proteolytic profile may exist. Methods: Levels of EMMPRIN, MT1-MMP, MMP-2, MMP-9, MMP-3, MMP-8, TIMP-1, and TIMP-2 were measured in aortic tissue and plasma from MFS patients with TAA and compared to healthy controls. Following modification of the abundance and location of MT1-MMP in isolated primary aortic fibroblasts, secreted EMMPRIN was measured in conditioned culture media. Results: Compared to controls, EMMPRIN is elevated in MFS TAA tissue and reduced in the plasma. Elevation of EMMPRIN abundance in tissue does not induce MMP-3, MMP-8, or TIMP-1 expression. MT1-MMP and TIMP-2 are elevated in MFS TAA tissue. MMP-2 and MMP-9 are reduced in MFS TAA tissue while increased in the plasma. In aortic fibroblasts we found that MT1-MMP must be internalized from the plasma membrane for EMMPRIN secretion. Conclusions: Our findings indicate that the pathological consequences of MFS cause the shedding of EMMPRIN and its secretion from cells to be blocked, which leads to higher EMPRINN abundance in MFS TAA tissue. This process depends upon the cellular location of MT1-MMP. Taken together, these observations suggest that internalization of MT1-MMP from the plasma membrane is required for the cellular secretion of EMMPRIN from aortic fibroblasts.