Clinical Characterization of Atypical Diabetes: Insights from the GENEPEDIAB Study into the Spectrum Between Type 1 and Monogenic Diabetes

BACKGROUND: Type 1 diabetes (T1D) shares clinical characteristics with other forms of diabetes, particularly monogenic diabetes such as maturity-onset diabetes of the young (MODY). Differential diagnosis is complicated by the existence of intermediate phenotypes. We aimed to delineate the phenotypic continuum between T1D and monogenic diabetes. METHODS: The multicentric GENEPEDIAB study included patients aged 6 months to 18 years diagnosed with diabetes and treated for either T1D or monogenic diabetes. Analyses comprised glycemic variability, continuous glucose monitoring metrics, application of the DIAMODIA criteria, and genetic investigations. RESULTS: A gradient was observed across T1D, atypical diabetes (Adia), and MODY cohorts for several glycemic parameters. T1D patients exhibited values furthest from treatment targets, whereas MODY patients showed better glycemic control. Stratification of the Adia cohort according to the number of positive DIAMODIA criteria further supported this trend, as demonstrated by glycemic measures and multiple correspondence analysis. Genetic analyses did not identify a uniform causative variant in the Adia cohort; however, several rare variants, including variants of uncertain significance and likely pathogenic variants in diabetes-related genes, were detected. CONCLUSIONS: These findings showed, in our specific cohort of pediatric patients, the existence of a phenotypic gradient between T1D and monogenic diabetes, with atypical diabetes occupying an intermediate position, including when stratified by DIAMODIA criteria.