Sitosterolemia (phytosterolemia): Diagnosis, treatment and prognosis

Sitosterolemia (phytosterolemia) is an inherited metabolic disorder characterized by the accumulation of plant sterols (phytosterols). The disease is caused by loss-of-function genetic mutations in sterolin proteins, which play an important role in selective excretion of plant sterols. Patients exhibit increased serum levels of phytosterols, total cholesterol and low-density lipoprotein cholesterol, which is accompanied by the risk of pre-mature atherosclerosis. Patients can have severe sitosterolemia when xanthomatosis develops as early as in infancy. Hematological disorders in the form of macrothrombocytopenia, stomatocytosis, episodes of hemolysis are reported in patients with sitosterolemia, which can be the only manifestation of the disease and are often interpreted as a manifestation of immune thrombocytopenia or primary hemolytic anemia. Hepatoand splenomegaly, acute liver failure, arthralgia may also be seen. Due to the similarity of clinical phenotypes, sitosterolemia can be misdiagnosed as familial hypercholesterolemia. It is vitally important to perform differential diagnosis to distinguish it from such diseases as lecithin-cholesterol acyltransferase deficiency, Tangier disease, cerebrotendinous xanthomatosis, familial dysbetalipoproteinemia, lysosomal acid lipase deficiency, primary biliary cirrhosis, storage diseases. The treatment of sitosterolemia in children includes the use of the intestinal cholesterol/phytosterol absorption inhibitor ezetimibe and bile acid sequestrant cholestyramine. The effective use of the combination of these drugs is described. The partial bypass of the distal ileum where the absorption of cholesterol, phytosterols, and reabsorption of bile acids mainly occurs can be used in severe cases. For patients with advanced vascular atherosclerosis and resistance to the standard treatments, LDL-C apheresis could be considered. The article describes our own clinical observation of a five-year-old patient suffering from sitosterolemia.