However, valvular abnormalities, which would be expected with an embryological disorder, are not described in affected Friesians.1 In human medicine, aortic rupture usually is preceded by aortic aneurysm formation, which is not the case in Friesians.7 In human patients, elastin and especially collagen have been shown to be important factors contributing to aortic aneurysm formation.8, 9 Collagen fibrils, together with smooth muscle cells and elastin, form the primary load‐bearing components of the aortic wall. This evidence concerns the gene ELN and aortic aneurysm.