MMP2 and aneurysm: Polymorphisms in eNOS, angiotensin-converting enzyme (ACE), and matrix metalloproteinase (MMP)-2 and -9 genes have also been associated with increased risk of aneurysm development in BAV patients by examining tissue samples of different segments of the aorta, suggesting the importance of considering the histological features of the whole AAo and the genetic risk profile of the patient [31].