You are examining a 17-year-old adolescent girl presenting with decreased range of motion, redness, and swelling of the joints due to arthritis. The young woman also presents with xanthomas in the Achilles tendon and extensor tendons of the hand. Additional examination indicates splenomegaly. Analysis of serum shows very high levels of sitosterol, campesterol, stigmasterol, and avenosterol. You suspect the patient is suffering from sitosterolemia. Which of the following class of transport systems is likely to be defective in this patient?

Question

Quizplus · Accepted Answer

Sitosterolemia is caused by mutations in the ABCG5 or ABCG8 genes, which encode for ABC transporters responsible for the efflux of plant sterols from enterocytes and hepatocytes.  Sitosterolemia is a rare autosomal recessively inherited disorder characterized by hyperabsorption and decreased biliary excretion of dietary sterols leading to hypercholesterolemia, tendon and tuberous xanthomas, premature development of atherosclerosis, and abnormal hematological and liver function test results. The disorder is caused by mutations in either of the 2 ABC transporter proteins of the obligate heterodimer composed of ABCG5 and ABCG8

You Are Examining a 17-Year-Old Adolescent Girl Presenting with Decreased