APOB and familial hypercholesterolemia: A pathogenic mutation at residue 3527 in APOB (apolipoprotein B), the specific ligand for binding of LDL to the LDLR, has been known for over two decades to cause the autosomal dominant condition familial defective apolipoprotein-B100 (FDB), a form of ADH (Soria et al. 1989), and a second variant in this region, Arg3558Cys, has also been associated with hypercholesterolemia (Pullinger et al. 1995).