Whereas KIR6.2 channels harboring mild gain of function mutations result in transient or permanent ND, strong gain of function mutant KIR6.2 channels on the other hand associate with a complex phenotype of developmental delay, muscle weakness, dysmorphic features, epilepsy and neonatal diabetes, known as the DEND syndrome (Hattersley and Ashcroft, 2005). The gene discussed is KCNJ11; the disease is Global developmental delay.