PCSK9 and familial hypercholesterolemia: The Consensus Panel on Familial Hypercholesterolemia of the European Atherosclerosis Society has previously stated that the general levels of LDL-C in double-heterozygous carriers of mutations in APOB, PCSK9, or LDLR to be less severely elevated as compared to homozygous carriers of variations in the same genes (Cuchel et al., 2014).