PCSK9 and familial hypercholesterolemia: Familial hypercholesterolemia (FH) is an autosomal codominant single-gene disorder caused by mutations in the LDL receptor (LDLR) gene, its ligand apolipoprotein (apo) B, or proprotein convertase subtilisin/kexin type 9 (PCSK9) that disrupt normal clearance of LDLs [1, 2].