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). Here, ABCC8 is linked to cartilage-hair hypoplasia.