Sterol and Isoprenoid Research Consortium (STAIR)

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Sitosterolemia

What is Sitosterolemia?

Sitosterolemia is a rare inherited plant sterol storage disease. Patients have significant increases of plant sterols (phytosterols) in blood and various tissues. Arteries and xanthomas (deposition of yellowish cholesterol rich material in tendons) in patients with sitosterolemia have increased amounts of these plant sterols including sitosterol, stigmasterol, and campesterol. Sitosterolemia is characterized by premature thickening of the artery walls due to plaque and fat build up.

Common Symptoms Include:

Who gets Sitosterolemia?

There have been approximately 80 patients worldwide diagnosed with Sitosterolemia. It can affect Individuals of all ages, ethnicities and sex.

What causes Sitosterolemia?

Normally we consume plant sterols in our diet. These plant sterols enter the intestinal cells, but then are pumped back out into the gut for disposal to keep plant sterols out of the body. Sitosterolemia is caused by a mutation or change in the ABCG8 and ABCG5 genes. These two genes code for proteins that pump plant sterols out of intestinal cells as well as liver cells. The mutations or changes in these genes lead to abnormal proteins that are unable to do their job correctly in the body. Therefore, high concentrations of plant sterols accumulate throughout the body.

Sitosterolemia is an inherited autosomal recessive genetic condition. Affected individuals inherit two copies of the mutated or changed ABCG8 or ABCG5 genes, one from each parent. Therefore the parents are "carriers" of Sitosterolemia, meaning that they have one normal functioning copy and one non functioning copy of the genes. With each pregnancy, carriers of Sitosterolemia have a 1 in 4 or 25% chance of having a child with the disease.

How is Sitosterolemia diagnosed?

Sitosterolemia is diagnosed by measurement of elevated plant sterols in the blood, including sitosterol, campesterol and stigmasterol. DNA mutation analysis of the ABCG5 and ABCG8 genes can be helpful in diagnostic confirmation, but such testing is not routinely available.

What is/is there treatment for Sitosterolemia?

Sitosterolemia can be managed by restricting plant sterols intake and by pharmacologic therapy. Dietary restriction may not be needed, if medications are employed. Ezetimibe is effective in reducing the plant sterol concentration in blood. There are some margarines and medications enriched with plant sterols that are often prescribed as a treatment for patients with hypercholesterolemia; it is important for patients with Sitosterolemia to avoid ingesting these preparations.