The PCSK9 variants are usually classified into 2 types: gain-of-function (GOF) and loss-of-function (LOF), where the GOF variant causes a decrease in LDLR on hepatocytes, leading to the phenotypes of FH, whereas the LOF is involved in the low LDL-C levels that lower the risk of developing coronary heart disease with no known adverse effects on human health (Bayona et al., 2020; Guo et al., 2020b). The gene discussed is LDLR; the disease is coronary artery disorder.