Cerebrotendinous xanthomatosis: The rare “treatable” disease you never consider

Cerebrotendinous xanthomatosis (CTX; Online Mendelian Inheritance in Man No. 213700) is an autosomal recessive disorder due to pathogenic variant in the CYP27A1 gene resulting in a defect in the mitochondrial enzyme sterol 27-hydroxylase.1 The enzyme catalyzes multiple hydroxylation reactions involved in cholesterol metabolism and bile acid synthesis. When affected, it results in decreased synthesis of bile acids, with the resultant production of cholestanol and cholesterol affecting all tissues.