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.

Aim To examine the hypoglycaemic effect on neurodevelopmental outcome in patients with transient and persistent congenital hyperinsulinism (CHI) born in the 21st century. Method A cohort of 117 patients (66 males, 51 females) with CHI aged 5 to 16 years (mean age 8y 11mo, SD 2y 7mo) were selected from a Finnish nationwide registry to examine all the patients with similar methods. Neurodevelopment was first evaluated retrospectively. The 83 patients with no risk factors for neurological impairment other than hypoglycaemia were recruited and 44 participated (24 males, 20 females; mean age 9y 7mo, SD 3y 1mo) in neuropsychological assessment with the Wechsler Intelligence Scale for Children, Fourth Edition and the Finnish version of the Developmental Neuropsychological Assessment, Second Edition domains of attention, language, memory, sensorimotor, and visual functioning. Results In retrospective analysis, transient and persistent CHI groups had similar prevalences of mild (22% and 18% respectively) or severe (5% and 7% respectively) neurodevelopmental difficulties. In clinical assessment, the neurocognitive profile was within the average range in both groups, but children with persistent CHI showed significant but restricted deficits in attention, memory, visual, and sensorimotor functions compared with the general population. The transient CHI group did not differ from the standardization samples. Interpretation Besides the more apparent broader neurological deficits, children with persistent CHI have an increased risk for milder specific neurocognitive problems, which should be considered in the follow‐up. What this paper adds Children with persistent congenital hyperinsulinism showed deficits in attention, memory, visual, and sensorimotor functions. The deficits were potentially of hypoglycaemic origin. Children with transient hyperinsulinism did not differ from the general population.

Context Major advances have been made in the genetics and classification of congenital hyperinsulinism (CHI). Objective To examine the genetics and clinical characteristics of patients with persistent and transient CHI. Design A cross-sectional study with the register data and targeted sequencing of 104 genes affecting glucose metabolism. Patients Genetic and phenotypic data were collected from 153 patients with persistent (n = 95) and transient (n = 58) CHI diagnosed between 1972 and 2015. Of these, 86 patients with persistent and 58 with transient CHI participated in the analysis of the selected 104 genes affecting glucose metabolism, including 10 CHI-associated genes, and 9 patients with persistent CHI were included because of their previously confirmed genetic diagnosis. Main outcome measures Targeted next-generation sequencing results and genotype–phenotype associations. Results Five novel and 21 previously reported pathogenic or likely pathogenic variants in ABCC8, KCNJ11, GLUD1, GCK, HNF4A, and SLC16A1 genes were found in 68% (n = 65) and 0% of the patients with persistent and transient CHI, respectively. KATP channel mutations explained 82% of the mutation positive cases. Conclusions The genetic variants found in this nationwide CHI cohort are in agreement with previous studies, mutations in the KATP channel genes being the major causes of the disease. Pathogenic CHI-associated variants were not identified in patients who were both diazoxide responsive and able to discontinue medication within the first 4 months. Therefore, our results support the notion that genetic testing should be focused on patients with inadequate response or prolonged need for medication.