It is characterized by hyperabsorption and decreased biliary excretion of dietary sterols (including the phytosterol beta-sitosterol).

Decreased range of motion with possible redness, swelling, and warmth of joints due to arthritis may be present.

Coronary heart disease and its health consequences are the primary causes of illness and premature death in untreated patients.

It has been shown to result from mutations in either of two adjacent and oppositely oriented genes (ABCG5 and ABCG8) located in chromosome 2 in band 2p21 and encode for ABC transporter proteins named sterolin-1 and sterolin-2, respectively.

[citation needed] The disorder is treated by strictly reducing the intake of foods rich in plant sterols (e.g., vegetable oils, olives, and avocados).

[citation needed] If dietary treatment alone is insufficient, bile acid-binding resins (e.g., cholestyramine, colestipol) could be considered.

In October 2002, a new cholesterol absorption inhibitor, ezetimibe, received US Food and Drug Administration (FDA) approval for use in sitosterolemia.

[citation needed] Finally, ileal bypass has been performed in select cases to decrease the levels of plant sterols in the body, though this therapy was undertaken before the advent of ezetimibe.