Pediatric Sitosterolemia: A Case Report and Literature Review

Sitosterolemia is a rare autosomal recessive disorder caused by pathogenic variants in ABCG5 or ABCG8, leading to increased intestinal absorption and reduced biliary excretion of plant sterols.We report a 13-year-old boy with severe hypercholesterolemia and poor response to high-dose atorvastatin.Targeted sequencing identified a pathogenic truncating ABCG8 variant (c.1974C>G; p.Tyr658*) and a second ABCG8 variant of uncertain significance (c.1570G>C; p.Gly524Arg).Plasma β-sitosterol was markedly elevated (35 mg/dL; reference 1.7-3 mg/dL), confirming the diagnosis.Atorvastatin was discontinued and treatment with ezetimibe 10 mg/day plus a phytosterol-restricted diet produced a rapid and substantial lipid improvement, with total cholesterol 124.5 mg/dL and LDL-cholesterol 59.9 mg/dL on follow-up, accompanied by clinical improvement.