Failure to synthesise normal bile acids reduces the flow of bile, causing cholestasis and the retention of potentially hepatoxic compounds – for example conjugated bilirubin – which are normally excreted in the bile.¹ Normally, bile acids facilitate the detachment of γ-glutamyl-transpeptidase (GGT) from the canalicular membrane. This is why BASDs, unlike other causes of cholestasis, do not lead to elevation of plasma GGT.¹ As taurine and glycine conjugates of cholic acid (CA) and chenodeoxycholic acid (CDCA) are required to facilitate emulsification and absorption of fats and fat-soluble vitamins, the absence of these bile acids can lead to steatorrhoea, failure to thrive and deficiencies of fat-soluble vitamins. ¹