Context: Major advances have been made in the classification and genetics of monogenic diabetes in infancy.
Objective: The objective of the study was to characterize different forms of diabetes diagnosed during the first year of life.
Design: Patients diagnosed with diabetes before the age of 1 year in 10 Finnish hospitals from 1980 to 2014 were included.
Setting: The study was conducted at Kuopio University Hospital and University of Eastern Finland.
Patients: Patients were identified through diagnosis-based searches from hospital registries including 93 children, of whom 64 participated.
Interventions: DNA sample for sequencing, serum sample, and medical records interventions were included.
Main outcome measures: Incidence of diabetes during the first year of life, sequencing results, human leukocyte antigen (HLA) genotypes, and islet autoantibodies were measured.
Results: The incidence of diabetes diagnosed during the first 12 months was 4.4/100 000/year. Three novel and 11 previously described mutations were found in 22 patients from 15 families in the KCNJ11, ABCC8, INS, GCK, FOXP, STAT3, and RFX6 genes. Positive islet autoantibodies were observed in 40.0% of the patients diagnosed during the first 0-6 months of life vs 70.8% of the patients diagnosed between ages of 7 to 12 months. A total of 85.7% of the patients carrying protective HLA genotypes were mutation-positive compared to 7.7% of the patients having high-risk genotypes (P = .001).
Conclusions: Mutations in the K-ATP channel and INS genes were the most common cause of early diagnosed monogenic diabetes. After 6 months of age, patients with diabetes had high HLA risk genotypes and islet autoantibodies, reflecting the autoimmune character of diabetes in that age group.