Mutations in genes encoding cholangiocyte ciliary-associated proteins, such as polycystin-1 and -2 and fibrocystin, cause biliary dysgenesis, hepatic fibrosis and cystogenesis in liver diseases such as Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Autosomal Recessive PKD (ARPKD). The gene discussed is PKHD1; the disease is autosomal dominant polycystic kidney disease.