CYP7B1 and cholestasis: Congenital bile acid synthesis disorder type 3 (CBAS3) is an extremely rare subtype caused by deficiency of oxysterol 7α-hydroxylase encoded by the cytochrome P450 7B1 (CYP7B1) gene [2], manifesting obvious cholestasis in the neonatal period with progressive aggravation and liver enlargement.