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Advanced case of sitosterolemia with a novel homozygous mutation

Taher Z, Ibrahim B, Saifaldeen R, Albar R

Sitosterolemia is a genetic lipid metabolic disorder characterized by increased intestinal absorption and decreased biliary excretion of plant sterols. The intestine and gallbladder work to balance plant sterols by ATP-binding cassette sub-family G member 5 and 8 proteins which are encoded by ABCG5 and ABCG8 genes. An eight year old girl who was misdiagnosed with familial hypercholesterolemia for two years, presented later with xanthoma, ecchymosis, easy tiredness, paleness, arthritis and abdominal pain. Her lab tests were: total cholesterol 5.3 mmol/L, hemoglobin 9.4 g/dL, platelet 160 × 1012/L, and CRP 15 mg/L. Specific testing for levels of sterols show very elevated levels of β-sitosterol, stigmastanol and campesterol. Genetic testing for ABCG5 and ABCG8 gene confirmed a novel mutation at ABCG8 gene (NM-022437.2). She was treated with ezetimibe 10 mg once daily. The symptoms disappeared after eight months of treatment although sterols were high. Her brother and sister were tested for β-sitosterol level as well as ABCG5 and ABCG8 gene mutation. Results of her brother and sister were positive for the diagnosis of sitosterolemia of the same mutation.