Sitosterolaemia

What else is it called?

  • Beta-Sitosterolaemia
  • Phytosterolaemia
  • Plant Sterol Storage Disease
  • Sitosterolemia

Get in touch

Contact our caring team on 08452 412 173 for help and support. Our phone lines open 10am-4pm, Monday to Friday.

Prefer to email? Our email address is contact@metabolicsupportuk.org.

What causes it?

This disorder is caused by a problem in either the ABCG5 gene or the ABCG8 gene. The genes are needed to produce the sterolin protein which is mainly found in the cells in our intestines and liver. This protein helps to remove plant sterols from our diet. We absorb plant sterols from plant-based foods and then because the cells in our body cannot use them, we excrete them in the gut. Sterolin also helps to regulate levels of cholesterol, a fatty substance found in animal products.

If not enough of the sterolin protein is made, the body cannot get rid of plant sterols (and less so, cholesterol) properly. Instead, they build up in the arteries and skin which lead to the symptoms of this disorder.

How common is it?

Between 80 and 100 cases have been reported worldwide. However, it is thought that some people who have this disorder may not be diagnosed.

What are the signs and symptoms?

Signs and symptoms often appear early in life after foods which contain plant sterols are introduced to the diet.  Symptoms vary, some people have either very few or no obvious symptoms at all. Symptoms may include:

  • High levels of plant sterols in the blood (30-100 times higher than normal)
  • Mildly elevated cholesterol levels
  • A build-up of fatty deposits in the arteries (atherosclerosis)
  • Yellow bumps under the skin (xanthomas) often affecting the buttocks, hips, elbows and knees or the tendons. Xanthomas may cause pain and difficulty with movement depending on their size.
  • Joint stiffness and pain
  • Abdominal pain
  • Arthritis
  • Enlarged spleen
  • Blood abnormalities
    • Premature break down of red blood cells causing low levels (haemolytic anaemia)
    • Unusual shaped red blood cells (stomacytes)
    • Low platelet count (thrombocyopaenia)
    • Large platelets or thrombocytes (macrothrombocytopaenia)

In some cases, blood abnormalities may be the only symptom.

If this condition is left untreated, those with atherosclerosis are at higher risk of heart attacks, stroke or sudden death due to the condition narrowing the arteries.

How is it diagnosed?

This disorder can be diagnosed by a specialised blood test to measure plant sterols in the blood. Genetic testing may be used to confirm the diagnosis.

Can it be treated?

Treatment is aimed at reducing the levels of plant sterols and cholesterol in the blood and to prevent xanthomas.  If you have this disorder you will need to follow a diet low in shellfish sterols (avoidance of shellfish) and low in plant sterols, such as those found in vegetable oils, margarine, nuts, seeds, avocado, and chocolate. You will also be given a medication (ezetimibe) to prevent/reduce the absorption of sterols. Other medications such as cholestrylamine may be considered if this is insufficient, alternatively an ileal bypass may be considered (shortening of the final part of the intestine). Treatment should help xanthomas to clear. All other treatment is based on providing relief for specific symptoms.

Do my family need to be tested?

Humans have chromosomes composed of DNA. Genes are pieces of DNA that carry the genetic instruction. Each chromosome may have several thousand genes. We inherit particular chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.

This is an inherited condition. There is nothing that could have been done to prevent it.

Everyone has a pair of genes that help to make the sterolin protein. If you have this disorder, neither of these genes works correctly. You will inherit one non-working gene from each parent. Parents of those with this disorder are carriers of the condition. Carriers do not have the disorder because the other gene of this pair is working correctly.

When both parents are carriers, in each pregnancy the risk to the baby is as follows:

  • 25% chance (1 in 4) of developing the disorder
  • 50% chance (1 in 2) for the baby to be a carrier of the disorder
  • 25% chance (1 in 4) for the baby to have two working genes and neither have the disorder nor be a carrier

Relevant Organisations

References

References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing helen@metabolicsupportuk.org [Resource Library No: SLL006].

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