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Conclusion:Gene polymorphism of the angiotensin-converting enzyme gene (ACE, I/D) does not predispose to aortoiliac occlusive disease (AIOD) but may be a factor in development of abdominal aortic aneurysm (AAA) when combined with hypertension.Summary: In 1992 Cambien et al noted an association between angiotensin-converting enzyme (ACE, I/D) gene polymorphisms with coronary artery disease and myocardial infarction. ACE levels in plasma and tissue are under genetic control, and about 50% of the ACE plasma level variability is associated with I/D gene polymorphism (Nature 1992;359: 641-4 and J Clin Invest 1990;86:1343-47). It is thought that an increase in ACE plasma levels affects angiotensin plasma levels, which can affect remodeling of vascular tissue in atherosclerosis. ACE D allele carriers have higher ACE plasma and tissue levels compared with those with I/D and II genotypes. ACE DD homozygotes have approximately twice higher levels of angiotensin 2 than do II homozygotes, with I/D individuals having intermittent ACE concentrations. The authors investigated 829 individuals with aortoiliac disease or controls. There were 133 patients with AAA, 152 with AIOPD, and a random Polish population of 392 patients who underwent ACE I/D gene polymorphism analysis. Analysis was performed by polymerase chain reaction and gel electrophoresis. Results indicated that genotype distribution and allele frequency of ACE I/D were not significantly different between patients with AAA or AIOD vs the control group. Differences were found in hypertensive patients with AAA vs normotensive patients with AAA (odds ratio, 3.05; 95% confidence interval, 1.22-7.79; P ϭ .015) and hypertensive patients with AAA vs the population group (odds ratio, 2.56; 95% confidence interval, 1.27-5.16; P ϭ .007). There was no relationship between ACE gene polymorphism and hypertension in the AIOD group.Comment: There have been mixed results analyzing the effects of polymorphisms of the ACE gene in the development of AAA. Patients in this study were Polish, whereas previous studies on Italian patients had suggested a stronger relationship between ACE polymorphism and development of AAA (Eur J Vasc Endovasc Surg 2001;21:445-50). Although there may be ethnic differences in susceptibility to polymorphisms of the ACE gene in the development of AAA, there are certainly many other unrecognized confounding variables and environmental factors that may also lead to these discrepant observations. Additional studies in other populations, considering environmental factors and perhaps ethnic variability, will be necessary to establish the role of the ACE gene in the development of AAA and the possible benefit of treatment with ACE inhibitors in patients at risk for AAA.