Congenital bile acid synthesis defect type 1 (BAS defect type 1) is the most common anomaly of bile acid synthesis characterized by variable manifestations of progressive cholestatic liver disease, and fat malabsorption. The disease is Monarch Disease Ontology entry MONDO_0011906 (congenital bile acid synthesis defect 1). Also known as: 3-beta-hydroxy-delta-5-C27-steroid oxidoreductase deficiency type 1, BASD1, CBAS1, HSD3B7 congenital bile acid synthesis defect, bile acid synthesis defect, congenital, type 1, congenital bile acid synthesis defect caused by mutation in HSD3B7, congenital bile acid synthesis defect type 1.