PCSK9 and familial hypercholesterolemia: In 2004, the discovery that hypermorphic or gain-of-function variants of PCSK9 cause familial hypercholesterolemia type III (MIM: 603776) (Timms et al., 2004) has led to the successful development and FDA approval of monoclonal antibodies against PCSK9, which are also used to treat non-familial forms of hypercholesterolemia (Blom et al., 2014; Roth et al., 2014; Cannon et al., 2015; Kereiakes et al., 2015).