Higher-Dose Ezetimibe to Treat Homozygous Sitosterolemia

This study will test the safety and effectiveness of 40 mg of ezetimibe (Zetia ) daily in lowering blood levels of cholesterol and of the plant sterols sitosterol and campesterol in patients with homozygous sitosterolemia, an inherited disorder of sterol metabolism. (Sterols are alcohol substances found in animal and plant fats.) In this disorder, an excess of many plant sterols is absorbed and not enough excreted. Patients can develop atherosclerosis and coronary heart disease as early as childhood, as well as other problems including arthritis, arthralgia, and tendon xanthomas (lipid deposits). Current treatment consists of ezetimibe 10 mg, dietary restriction of plant and shellfish sterols, and bile salt binding resins. Ezetimibe is a cholesterol-lowering drug that inhibits intestinal absorption of cholesterol and structurally related plant sterols across the intestinal wall. Patients with homozygous sitosterolemia who are between 18 and 85 years of age have completed NHLBI's 1-year study of ezetimibe at 10 mg a day may be eligible for this study. All participants maintain their current stable diet and take a 10-mg pill of ezetimibe daily for 26 weeks. They are also randomly selected to take either an additional 30-mg pill of ezetimibe or a placebo (look-alike pill with no active ingredients). Patients fast for at least 12 hours before each of 6 visits scheduled during the course of the study. At these visits, patients undergo some or all of the following procedures for monitoring their health and evaluating their response to treatment: * Medical history and review of medications * Physical examination * Measurement of vital signs (pulse rate, blood pressure, breathing rate and temperature) * Review of dietary maintenance * Measurements of height, weight, and waist circumference * Measurement (with ruler) and photographs of non-Achilles xanthoma * X-ray of Achilles tendon * Blood draw and urine collection * Pregnancy test for women of childbearing potential