Genetic variants of collagen III and abdominal aortic aneurysm.

Collagens provide the tensile strength of the aortic wall. Variations in collagen structure are recognised in Ehlers Danlos syndrome type IV and could also be associated with a predisposition to aortic aneurysm. The frequency of some minor genetic variants of type III collagen, present in the normal population, can be detected by restriction enzyme digestion of genomic DNA from peripheral leucocytes. The frequency of a minor collagen type III allele demonstrated with the restriction enzyme Ava II was compared in patients with abdominal aortic aneurysm (n = 70) and aortoiliac stenosis (n = 47). The frequency of the minor allele was significantly higher in aneurysm patients (0.30) compared with patients with aortoiliac stenosis (0.17), p less than 0.05. The presence of the minor allele was associated with a less elastic aneurysm wall (median pressure strain elastic modulus 4575, n = 7), compared with patients homozygous for the common allele (median pressure strain elastic modulus 1990, n = 6), p less than 0.05. These results indicate that genetic variants of type III collagen may influence the extensile properties of the aortic wall and that mutations in the type III collagen gene may be associated with aortic aneurysms.