defect in cholesterol 7α-hydroxylase
The defect in the key enzyme of the classical pathway of bile acid synthesis, cholesterol 7α-hydroxylase (CYP7A1), has been associated with a decrease in bile acid production via the classical pathway, which is compensated by activation of the alternative acidic pathway. In these individuals, hepatic cholesterol contents are increased and, in adults, LDL hypercholesterolemia and cholesterol gallstones are commonly present. However, usually there is no evidence of liver disease.