The most severe forms of CHH are due to defects in the genes (ABCC8 and KCNJ11), which encode for the sulfonylurea receptor protein (SUR1) and inwardly rectifying potassium channels (Kir6.2) proteins, respectively, of the potassium sensitive KATP channel (7, 8). This evidence concerns the gene KCNJ11 and cartilage-hair hypoplasia.