Endocrine Abstracts

Background and aims

Monogenic forms of diabetes caused by a single gene defect include maturity onset diabetes of the young (MODY), neonatal diabetes mellitus and syndromic forms. They are estimated to account for 1–3% of all diabetes cases, but the prevalence is higher among pediatric patients without islet autoantibodies (AAB). Despite presenting with insulin deficiency, many patients can be treated with anti-hyperglycaemic agents to stimulate their insulin secretion. Our main objective was to assess the prevalence and clinical manifestations of monogenic diabetes in pediatric patients who were AAB-negative or positive only for low titer islet cell antibodies (ICAs) at diagnosis.

Materials and methods

At diagnosis, 6484 patients were tested for AAB through the Finnish Pediatric Diabetes Register, which covers approximately 90% of newly diagnosed diabetic patients aged < 16 years in Finland. Only 174 patients (3%) tested negative for all five AAB (ICAs, IAA, GADA, IA-2A and ZnT8A) and 58 patients (0, 9%) had only low titer ICAs (< 10RU). DNA samples were available for 214 patients. A next generation sequencing (NGS) gene panel including 42 genes associated with monogenic diabetes (exons ± 50 nucleotides, and promoter regions harboring known pathogenic variants) was used for the detection of monogenic diabetes.

Results

We identified a monogenic cause for diabetes in 20 patients negative for all five AAB, accounting for 12% of the AAB-negative patients and 0, 3% of all 6484 children in our cohort (n = 4 mutations in GCK, n = 6 mutations in transcription factors HNF1A, HNF4A or HNF1B, n = 4 mutations in INS, n = 6 rare monogenic forms caused by mutations in KCNJ11, RFX6, LMNA and WFS1). At diagnosis, the median [IQR] age was 9.3 [6, 6–13, 8] years and the median ISO-BMI was 20.2 [17, 7–25, 2] kg/m². None of these 20 patients had presented with ketosis or ketoacidosis at diagnosis and none carried a high-risk HLA susceptibility genotype for type 1 diabetes. So far, two of these patients have been successfully transferred from insulin to oral treatment. The screening results of patients with low ICAs will be presented at e-ECE 2021.

Conclusion

A monogenic cause for diabetes was found in 12% of the AAB-negative patients screened by the NGS gene panel. As AAB-negative patients account for only approximately 3% of all diagnosed pediatric patients in Finland, screening of all AAB-negative pediatric patients for monogenic diabetes should be considered.