The molecular rationale for the positive 68Ga-DOTA-exendin-4 PET was found in the performed autoradiography study that demonstrated a more than 3-time higher density of GLP-1R in the islets of this nesidioblastosis patient when compared with islets of a normal pancreas (Christ et al. 2015). The gene discussed is GLP1R; the disease is familial hyperinsulinism.