 Mutations in both alleles of either ABCG5 or ABCG8 in the human results in sitosterolemia.Sitosterolemia (also known as phytosterolemia) is a rare autosomal recessively inherited lipid metabolic disorder characterized by the presence of tendon xanthomas, premature coronary artery disease and atherosclerotic disease, hemolytic episodes, arthralgias and arthritis.The hallmark of sitosterolemia is diagnostically elevated levels of plant sterols in the plasma.