As reported in the literature, the proportion of neonatal diabetes cases attributed to monogenic causes is around 50% (9); and about 3% of cases of permanent neonatal diabetes mellitus with permanent insulin requirement due to pancreatic agenesis are attributed to pathogenic variants of the PDX1 gene, either in homozygosis, that is, the same variant in both alleles, or compound heterozygosis, understood as the presence of two different variants each in a gene locus (2), the latter being the one presented by the two brothers reported. The gene discussed is PDX1; the disease is neonatal diabetes mellitus.