Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive inborn lipid storage disorder due to enzyme sterol 27-hydroxylase deficiency resulting in impaired bile primary acid synthesis, increased concentration of bile alcohols and increased accumulation of both cholestanol and cholesterol in plasma and in various tissues, particularly in the nervous system [182]. This evidence concerns the gene CYP27A1 and cerebrotendinous xanthomatosis.