Sitosterolemia
Synonyms
1
Overview
Sitosterolemia (also known as phytosterolemia) is a rare autosomal recessively inherited lipid metabolic disorder. It is characterized by hyperabsorption and decreased biliary excretion of dietary sterols leading to hypercholesterolemia, tendon and tuberous xanthomas, premature development of atherosclerosis, and abnormal hematologic and liver function test results.
Symptoms
Sitosterolemia shares several clinical characteristics with the well-characterized homozygous familial hypercholesterolemia (FH), such as the development of tendon xanthomas in the first 10 years of life and the development premature atherosclerosis . However, in contrast to FH patients, sitosterolemia patients usually have normal to moderately elevated total sterol levels and very high levels of plant sterols (sitosterol, campesterol, stigmasterol, avenosterol) and 5α-saturated stanols in their plasma. Plasma sitosterol levels in sitosterolemia patients are 10–25 times higher than in normal individuals (8–60 mg/dl). Xanthomas may appear at any age, even in childhood. These may be present as subcutaneous xanthomas on the buttocks in children or in usual locations (eg, Achilles tendon, extensor tendons of the hand) in children and adults.Xanthelasma and corneal arcus are less common.Decreased range of motion with possible redness, swelling, and warmth of joints due to arthritis may be present.In addition, sitosterolemia patients may develop hemolytic episodes and splenomegaly. Untreated, the condition causes a significant increase in morbidity and mortality. Coronary heart disease and its inherent health consequences are the primary causes of illness and premature death in untreated patients
Treatment
The disorder is treated by strictly reducing the intake of foods rich in plant sterols (e.g., vegetable oils olives and avocados). If dietary treatment alone is insufficient,bile acid-binding resins (eg, cholestyramine, colestipol) or competitive inhibitory agents (eg, sitostanol) could be considered. In October 2002, a new cholesterol absorption inhibitor, ezetimibe, received US Food and Drug Administration (FDA) approval for use in sitosterolemia. Because the mechanism by which it inhibits cholesterol absorption is quite specific. Finally, ileal bypass has been performed in select cases to decrease the levels of plant sterols in the body.