HNF1B and autosomal recessive polycystic kidney disease: There is also the possibility that some of the patients without 2 causal mutations in PKHD1 harbor a mutation located within its intronic region, with an impact on gene expression and/or mutations in other genes (e.g., PKD1, PKD2, HNF1β, etc.)that could cause a severe renal and/or hepatic phenotype resembling ARPKD.