So far, approximately 40 patients with CHH resulting from a mutation in the HADH gene have been reported (Table 1) (3,4,5,6,7,8,9,10,11,12,13,14,15).The mechanism behind unregulated insulin secretion in SCHAD deficiency is currently not understood but may involve changes in protein-protein interactions with glutamate dehydrogenase (GDH) (16,17). Here, GLUD1 is linked to cartilage-hair hypoplasia.