Cholestanol is a cholesterol metabolite formed by oxidation and an intermediate in the biosynthesis of chenodeoxycholic acid .¹ Cholestanol (10 µg/ml) induces apoptosis in cornea and lens epithelial cells and increases the activity of IL-1β converting enzyme (ICE) and CPP32 proteases.² Dietary administration of 1% cholestanol to mice increases serum and liver cholestanol levels and leads to corneal opacities and gallstones and in rats it leads to cholestanol deposition in the cerebellum.³ Cholestanol levels are increased in plasma of patients with cerebrotendinous xanthomatosis (CTX), a disease characterized by a deficiency in the mitochondrial enzyme sterol 27-hydrolylase (CYP27A1) that leads to progressive neurological symptoms.⁴