Bile acids are end products of cholesterol metabolism. Individuals with inborn errors of bile acid synthesis lack the enzymes needed to synthesize the primary bile acids cholic acid and chenodeoxycholic acid (CDCA). These conditions are serious and account for approximately 1% of cases presenting as idiopathic cholestatic liver disease. The liver disease associated with these inborn errors in bile acid synthesis is progressive and, if untreated, may lead to death from cirrhosis and liver failure.