PCSK9 and familial hypercholesterolemia: PCSK9 is the third gene implicated in familial hypercholesterolemia (FH3) because of its ability to target the low-density lipoprotein receptor (LDLR) to lysosomes for degradation in a non-enzymatic fashion [2], thereby increasing the circulating levels of LDL-cholesterol (LDLc) [3,4].