P-393: Not all type 1 diabetes is type 1: a pediatric case of HNF1A-MODY
B de Melo Nunes, A Alves Cabral, I Aguiar Paiva, K de Souza Oliveira, L Ignachiti Francisco, B Barone, J Veiga Moreira Vasconcellos, D Christian de Arruda Costa, J Elmor Mainczyk, L Salomão TyszlerAbstract
Introduction
Maturity-onset diabetes of the young (MODY) is often misclassified as type 1 diabetes (T1D) in pediatric patients. HNF1A-related MODY is characterized by progressive beta-cell dysfunction and marked sensitivity to sulfonylureas, often allowing insulin discontinuation
Objectives
To highlight the clinical and therapeutic impact of genetic diagnosis of MODY in a pediatric patient initially misclassified as T1D.
Methods
Retrospective review of clinical, laboratory, and genetic data from a pediatric patient with diabetes mellitus followed at a tertiary care center.
Results
A male patient was diagnosed with diabetes mellitus at 9 years of age after presenting with polyuria, polydipsia, weight loss, and capillary glucose >200 mg/dL. He was initially classified as having T1D and started on insulin therapy.
Despite progressive intensification, insulin requirements remained low for age and disease duration (<0.5 U/kg/day). Autoimmune markers were negative, and C-peptide remained preserved (1.1 ng/mL) five years after diagnosis. Family history revealed diabetes across multiple generations, including individuals not requiring insulin therapy.
HbA1c ranged from 5.4% to 6.8% during the first four years after diagnosis, later increasing to 7.3%. Genetic testing identified a pathogenic variant in HNF1A, confirming HNF1A-MODY.
Insulin therapy was discontinued and gliclazide 30 mg daily was initiated. HbA1c decreased from 7.3% to 5.3% within three months and remained stable (5.7–5.9%) during follow-up, with no episodes of hypoglycemia reported.
Conclusions
Recognition of MODY in children with atypical features of T1D enables precision treatment, improves glycemic control, and avoids unnecessary insulin therapy.