COMP and triple-A syndrome: As shown in our previous studies, COMP maintains vascular homeostasis and inhibits atherosclerosis, vascular calcification and thrombosis.25–28 We first designed a matched case-control study with matched gender frequency and comparable age distribution (Supplementary information, Table S1) in 88 cases (patients with AAA) and 88 controls (patients with arteriosclerosis obliterans of the lower limbs (ASO), but not AAA) to measure the plasma COMP levels and further investigated whether COMP is involved in the AAA etiology.