APOB and familial hypercholesterolemia: At the same time, Abifadel et al. [2] described two gain-of-function mutations in the PCSK9 gene causing autosomal dominant hypercholesterolemia in two French families without mutations in the typical candidate genes responsible for familial hypercholesterolemia, the low-density lipoprotein (LDL) receptor (LDLR) and apolipoprotein B (apoB).