Mutations causing MODY have been described in at least 13 genes: HNF4A, GCK, HNF1A, IPF1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, and KCNJ11 [2–4]. The gene discussed is GCK; the disease is MODY.