Christesen HBT et al. - This is the first report to highlight a genetic cause to adult-onset NI-PHH/NIPHS. The activating GCK mutation was dominantly inherited, but only after year-long follow-up and investigations, other family members were diagnosed symptomatic. Hypoglycaemia unawareness seems to be a prominent feature, but hypoglycaemic attacks occur after slimming, especially postprandially. PHH-GCK was medical responsive.