ATP8B1 and progressive familial intrahepatic cholestasis type 1: Mutations in ATP8B1 (18q21-q22) cause variable cholestatic phenotypes ranging from progressive to benign recurrent forms (Progressive Familial Intrahepatic Cholestasis type 1, PFIC1, formerly Byler disease, and Benign Recurrent Intrahepatic Cholestasis type 1, BRIC1; OMIM 211600, 243300) [1], [2].