APOE and Hypercholesterolemia: Further, gene variants, including apolipoprotein E (APOE) isoforms, and single-nucleotide polymorphisms in genes encoding the LDL-receptor (LDL-R), apolipoprotein B (apoB), and proprotein convertase subtilisin/kexin type 9 (PCSK9) may result in severe hypercholesterolemia and hypertriglyceridemia [26,27].