Recently, individuals with MFS have been shown to have dysregulation of transforming growth factor beta (TGF-beta) signaling that is postulated to result in the enlarged aortic root and other manifestations of the disease. Conversely, disorders of TGF beta 1 and 2 receptors have been shown to produce a Marfan phenotype. A study using a Marfan mouse model found that Losartan, an angiotensin 2 AT1 receptor blocker, prevented the development of aortic root dilation and other phenotypic manifestations of the syndrome. Among the actions of Losartan is the prevention of increased levels of TGF beta and its effects on stimulation of production of extracellular matrix in vascular smooth muscle. This evidence suggests that agents that alter TGF beta signalling, such as Losartan, might have significant potential to ameliorate endothelial dysfunction and aortic dilation in MFS. A clinical trial comparing the effects of Losartan with the current standard treatment regimen (beta blockers) is needed.