Congenital bile acid synthesis defect type 3 (BAS defect type 3) is a severe anomaly of bile acid synthesis (see this term) characterized by severe neonatal cholestatic liver disease. The disease is Congenital bile acid synthesis defect type 3 (Orphanet_79302, an Orphanet rare-disease nomenclature entry). Also known as: Oxysterol 7-alpha-hydroxylase deficiency.