PCSK9 and sitosterolemia: In sitosterolemia, dietary treatment results in an important reduction in cholesterol values, however, the effect of dietary intervention on familial hypercholesterolaemia (FH) is small (10–12% from baseline); similarly, the use of drugs such as cholestyramine and/or ezetimibe leads to normalisation of plasma total cholesterol and LDL cholesterol values in sitosterolemia, whereas FH usually requires combined treatment with statins and ezetimibe or proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors.