Sitosterolemia is an autosomal recessive disorder characterized by increased intestinal absorption of plant sterols. It is caused by mutations in genes encoding ATP-binding cassette, subfamily G5 (ABCG5) or G8 (ABCG8), and clinical features include elevated plant sterol levels, xanthomas, and accelerated atherosclerosis. Although it was originally reported in patients with normolipemic xanthomas, patients with sitosterolemia also hyperabsorb cholesterol, and serum cholesterol levels tend to be elevated.