PFIC1, a type of progressive familial intrahepathic cholestasis (PFIC), is an infantile hereditary disorder in bile formation that is hepatocellular in origin and associated with extrahepatic features. The disease is Monarch Disease Ontology identifier MONDO_0008892 (progressive familial intrahepatic cholestasis type 1). Also known as: Byler disease, FIC1 deficiency, PFIC1, cholestasis, progressive familial intrahepatic 1, cholestasis, progressive familial intrahepatic, type 1.