Fytosterolemie

Fytosterolemie, also known as phytosterolemia or phytostanolremia, is a rare autosomal recessive genetic disorder characterized by extremely high levels of plant sterols, such as sitosterol and campesterol, in the blood and tissues. This condition is caused by mutations in the ABCG5 and ABCG8 genes, which encode for ATP-binding cassette transporters responsible for mediating the efflux of dietary and biliary sterols from intestinal and hepatic cells back into the intestinal lumen. When these transporters are defective, plant sterols are absorbed and retained in the body, leading to their accumulation.

The hallmark clinical manifestation of fytosterolemie is xanthomas, which are yellowish deposits of lipids in the skin and tendons, particularly around the eyes (xanthelasma) and in the extensor surfaces of limbs. A significant consequence of this disorder is premature atherosclerosis and cardiovascular disease. The elevated levels of plant sterols can interfere with cholesterol metabolism, promote oxidative stress, and contribute to the development of plaques in arteries, often leading to early onset heart attacks and strokes.

Diagnosis is typically made through a combination of clinical presentation, family history, and laboratory tests revealing markedly elevated plasma concentrations of plant sterols, often exceeding 10-20 times the normal range, while cholesterol levels may be normal or only slightly elevated. Genetic testing can confirm the diagnosis by identifying mutations in the ABCG5 or ABCG8 genes.

Treatment primarily involves dietary intervention and pharmacotherapy. A low-fat diet with significantly reduced intake of plant sterols and stanols is crucial. Medications such as ezetimibe, which inhibits intestinal sterol absorption, and statins, which lower cholesterol synthesis, are also effective in reducing plasma phytosterol levels and mitigating cardiovascular risk. Early diagnosis and aggressive management are essential to prevent severe complications.