Healthy Individuals Carrying the PCSK9 p.R46L Variant and Familial Hypercholesterolemia Patients Carrying PCSK9 p.D374Y Exhibit Lower Plasma Concentrations of PCSK9

The loss-of-function p.R46L variant is associated with the expected lower concentrations of circulating PCSK9; the gain-of-function p.D374Y mutation is also associated with lower concentrations, presumably because of the higher affinity of this variant for the LDL receptor and its more rapid clearance. In treated FH patients, a low plasma PCSK9 concentration does not appear to be a useful screening tool for identifying novel PCSK9 mutations.