ARPKD is caused by dysfunction of primary cilia15 due to mutations within polycystic kidney and hepatic disease-1 (PKHD1), which encodes a 4074 amino acid multi-domain transmembrane protein (fibrocystin/polyductin, FPC) that is expressed in the primary cilia of renal tubular epithelial cells and cholangiocytes16,17. The gene discussed is PKHD1; the disease is glycogen storage disease VI.