Maturity onset diabetes of the young due to damaging alleles in hepatocyte nuclear factor-1 alpha (HNF1A-MODY) is a rare type of diabetes caused by an autosomal-dominant mutation in the single gene, HNF1A, which is involved in regulating β-cell development and insulin secretion (Cardenas-Diaz et al. The gene discussed is HNF1A; the disease is diabetes mellitus.