The extension of HIPKD’s spectrum of disease to include the GI tract is consistent with this hypothesis since HNF4A expression seems to reflect all the organ pathology seen in PMM2-related disease, i.e. kidney (polycystic kidney disease), pancreatic (hyperinsulinaemic hypoglycaemia), liver (hepatic cysts), gastric (foveolar hyperplasia), and intestinal tissue (inflammatory bowel disease) (Fig. 2b) (Uhlen et al. 2015). Here, PMM2 is linked to polycystic kidney disease.