Sitosterolemia: A genetic disease involving lipids (fats) in which there is excessive intestinal absorption of dietary sterols and impaired clearance of these sterols from the liver into the bile. These sterols include cholesterol and the plant sterol sitosterol (from which comes the name of the disease). Patients with the disease have abnormally high blood levels of sterols and a tendency to develop coronary artery disease at an unusually early age (in the teens). The high blood fat levels also lead to abnormal red blood cells (causing chronic anemia) and fatty deposits (xanthomas) on tendons.
Sitosterolemia is inherited as a rare autosomal recessive condition. It affects males and females alike. It is caused by mutations in ABCG5 and ABCG8, two adjacent and oppositely oriented genes located in chromosome 2 in band 2p21. These two genes, ABCG5 and ABCG8, encode proteins with homology (similarity) to genes known as the "ATP binding cassette (ABC) transporters" which are also involved in cholesterol transport.
The disorder is treated by strictly limiting cholesterol in the diet, reducing the intake of foods rich in plant sterols (e.g., vegetable oils) and giving cholestyramine resin to promote sterol excretion from the body.