Congenital bile acid synthesis defect type 2 (BAS defect type 2) is an anomaly of bile acid synthesis characterized by severe and rapidly progressive cholestatic liver disease, and malabsorption of fat and fat-soluble vitamins. The disease is congenital bile acid synthesis defect 2 (MONDO_0009339, a Monarch Disease Ontology identifier). Also known as: AKR1D1 congenital bile acid synthesis defect, BASD2, CBAS2, bile acid synthesis defect, congenital, type 2, cholestasis with delta(4)-3-oxosteroid 5-beta-reductase deficiency, congenital bile acid synthesis defect caused by mutation in AKR1D1, congenital bile acid synthesis defect type 2.