[Congenital deficiencies in bile acid synthesis: from diagnosis to treatment]

Bile acids represent the principal excretion pathway of cholesterol. Their synthesis involves hydroxylations of the sterol nucleus and shortening of the lateral chain transforming an highly insoluble and immiscible molecule in an hydrophilic and detergent one. Congenital defect of one of the enzymes of bile acid synthesis (26-alpha-hydroxylase) constitutes the etiology of cerebrotendinous xanthomatosis, associating degenerative disease of the central nervous system, cutaneous xanthomas and cataract; the degenerative process may be stopped by a substitutive therapy with chenodeoxycholic acid. In another syndrome characterised by a lack of peroxisomes (Zellweger disease and associated syndromes), some bile acid metabolites accumulate due to the enzymatic block. Some cases of malabsorption due to a congenital defect of bile sterol synthesis are reported; such a case was jointly investigated in Brussels and Groningen.