LDLR and familial hypercholesterolemia: In most cases, familial hypercholesterolemia develops in the presence of pathogenic variants of genes encoding the low-density lipoprotein receptor (LDLR), its ligand apolipoprotein B (APOB), or the proprotein convertase subtilisin/kexin type 9 (PCSK9), which takes part in the regulation of cholesterol metabolism.