Supplementary Material for: Neonatal diabetes in Ireland over the past 19 years: Clinical presentation, management, genetics, and outcomes

Background: Neonatal diabetes mellitus (NDM) is a rare monogenic form of diabetes presenting before 6 months of age. It may be permanent (PNDM) or transient (TNDM). Individuals with KATP channel variants may respond to oral sulphonylurea instead of insulin. Aim: To review the presentation, genotype, phenotype, management and outcomes of patients diagnosed with NDM in Ireland over 19 years. Methods: Data on Irish NDM cases from 2006-2024 were collated through Paediatric Endocrinologists nationally and electronic databases. Analyses were performed using SPSS, with ethical approval obtained. Results: Nineteen cases were identified: twelve PNDM and seven TNDM. Age at diagnosis ranged from 1 day to 11 months. Among PNDM cases, KCNJ11 (n=6), EIF2AK3 (n=3) and INS (n=1) variants were identified, while two lacked a genetic diagnosis. Six TNDM cases had 6q24 methylation defects, and one had an ABCC8 variant. Genetic diagnosis informed familial risk and prompted changes to a parent’s medical management. Sulphonylurea therapy was most effective when initiated early. Conclusions: This national case series highlights the genetic and phenotypic spectrum of NDM in Ireland. Early genetic diagnosis enables precision therapy, with timely sulphonylurea initiation improving outcomes in KATP-related NDM.