Pathogenic or likely pathogenic mutations in ATP8B1, ABCB11, ABCB4 and TJP2 genes can be responsible for 21% of idiopathic cholestasis in young and adult patients: they have higher rates of cholestatic histological features, higher levels of liver fibrosis and serum BAs compared to the subjects without, at least likely, pathogenic mutations [1]. The gene discussed is ABCB4; the disease is Hepatic fibrosis.