Familial hypercholesterolemia (FH) is an autosomal hereditary disorder characterized by elevated plasma LDL cholesterol levels. This disease is notable for clearly establishing the molecular pathological connection between cholesterol and atherosclerosis, as elucidated by the pioneering research of Goldstein and Brown (1979) who discovered the genetic mutations in the LDL receptor. In homozygous FH, the mutations in the LDL receptor and other genes correlated with the LDL receptor pathway lead to a marked increase in plasma LDL cholesterol levels. As a result, severe atherosclerosis develops from a young age, and many patients experience ischemic heart disease in adolescence. Further research has also revealed that modified, denatured LDL is taken up by macrophages, leading to the formation of foam cells (Goldstein et al. 1979). The receptors involved in this process have been identified, elucidating the molecular pathological mechanisms underlying foam cell formation and LDL accumulation in the arterial wall (refer to Chap. 7 ).