Firstly, a recessive disorder known as sitosterolemia, where mutations in the ABCG5 and ABCG8 genes are probably involved, consists of an increased absorption and decreased excretion of phytosterols and cholesterol, and results in elevated serum concentrations of phytosterols, which might manifest as tendon and tuberous xanthomas and premature coronary atherosclerosis [67]. The gene discussed is ABCG8; the disease is sitosterolemia.