Sitosterolemia 1

Any sitosterolemia caused by a variation in the ABCG8 gene, characterized by increased intestinal absorption and reduced biliary excretion of plant sterols, leading to markedly elevated plasma sitosterol and related phytosterols, xanthomas, and premature atherosclerosis/coronary disease. Some patients develop hematologic manifestations, including stomatocytic hemolysis, macrothrombocytopenia, splenomegaly, and abnormal bleeding. In some cases the hematologic phenotype can be the presenting or only sign. Biallelic loss‑of‑function variants in ABCG8 impair the heterodimeric transporter that normally limits sterol absorption and promotes biliary sterol excretion, explaining the biochemical and clinical findings.