GCK and diabetes mellitus: Although more than 30 genes have been associated with monogenic diabetes [11], population studies using NGS in patients with young-onset diabetes [6] and in adults [7, 12] have consistently shown that three genes (GCK, HNF1A, and HNF4A) account for the large majority of MODY cases, one (HNF1B), associated with renal features, is less frequently involved, and three others (ABCC8, KCNJ11, and INS) are rare causes.