CYP27A1 and cerebrotendinous xanthomatosis: Cerebrotendinous xanthomatosis CTX is a neurometabolic storage disorder caused by mutations in the CYP27A1 gene, mapped on chromosome 2q33 and codifying for the 27-hydroxylase, with mutations that lead to reduced enzymatic activity and elevated levels of cholestanol, cholesterol, and bile alcohols [121].