[Physiopathology of aortic aneurysm].

Aneurysm is an arterial dilatation with risk of rupture. It is a disease of the media characterized by the destruction of extracellular matrix proteins (especially elastin) involving different proteases: matrix metalloproteinases, fibrinolytic proteases (plasminogen activators, plasmin), leucocyte elastase, and by the absence of scarring process. There is an imbalance in the aortic wall between proteolytic and antiproteolytic activities, the former being overexpressed (by inflammatory cells infiltrating the aortic wall on the adventitial side, and the endoluminal thrombus), the latter (normally synthesized and secreted by vascular smooth muscle cells) being decreased in relation to the disappearance of smooth muscle cells.