HNF4A and MODY: Maturity-onset diabetes of the young (MODY) is a rare monogenic type of diabetes mellitus with autosomal dominant inheritance and includes 14 subtypes, which are classified by causative genes: HNF4A, GCK, HNF1A, NEUROD1, PDX1, HNF1B, KLF11, CEL, PAX4, INS, BLK, KCNJ11, ABCC8, or APPL1 [1].