AOPEP and arterial disorder: Although most genetic association studies investigating the potential discordance between the apo(a) isoform size and Lp(a) levels on the artery disease risk provided evidence for a causal role of Lp(a) levels in artery disease independent of the apo(a) isoform size, a Mendelian randomization analysis provided evidence that a variant linked to a smaller apo(a) isoform size, though not to Lp(a) levels, is associated with artery disease [77].