CYP27A1 and cerebrotendinous xanthomatosis: Cerebrotendinous xanthomatosis (CTX), a rare autosomal recessive cholestanol lipidosis, is caused by a deficiency of the gene encoding the mitochondrial sterol 27-hydroxylase (CYP27A1) [1-4] and subsequently results in an abnormal deposition of cholestanol and cholesterol in various organs.