MMP9 and Marfan syndrome: It is known that the complex pathogenesis of MFS involves an imbalance in expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMP activity.42 More specifically, Mmp2, Mmp9 and Mmp12 have been shown to be up‐regulated in mgR/mgR mice.43 We identified the same trend in Mmp12 expression.