PCSK9 and familial hypercholesterolemia: Variants in genes that regulate low-density lipoprotein (LDL) levels, such as LDL receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9), can markedly elevate LDL concentrations, as observed in familial hypercholesterolemia, a monogenic disorder associated with early and aggressive plaque formation [21,22,23].