Variants in genes encoding extracellular matrix–degrading enzymes, such as matrix metalloproteinases (MMP-2, MMP-9), as well as polymorphisms in genes regulating inflammatory cytokines, including interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), have been associated with increased AAA susceptibility [27,28]. Here, MMP9 is linked to triple-A syndrome.