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.

Context The management of congenital hyperinsulinism (CHI) has improved. Objective To examine the treatment and long-term outcome of Finnish patients with persistent and transient CHI (P-CHI and T-CHI). Design A population-based retrospective study of CHI patient treated in 1972-2015. Patients 106 patients with P-CHI and 132 patients with T-CHI (altogether, 42 diagnosed before and 196 after year 2000) with a median follow-up times of 12.5 and 6.2 years, respectively. Main outcome measures Recovery, diabetes, pancreatic exocrine dysfunction, neurodevelopment. Results The overall incidence of CHI (n = 238) was 1:11 300 live births (1972-2015). In 2000-2015, the incidence of P-CHI (n = 69) was 1:13 500 and of T-CHI (n = 127) 1:7400 live births. In the 21 st century P-CHI group, hyperinsulinemic medication was initiated and normoglycemia achieved faster compared to earlier. Of the 74 medically treated P-CHI patients, 68% had discontinued medication. Thirteen (12%) P-CHI patients had partial pancreatic resection and 19 (18%) underwent near-total pancreatectomy. Of these, 0% and 84% developed diabetes and 23% and 58% had clinical pancreatic exocrine dysfunction, respectively. Mild neurological difficulties (21% vs 16%, respectively) and intellectual disability (9% vs 5%, respectively) were as common in the P-CHI and T-CHI groups. However, the 21 st century P-CHI patients had significantly more often normal neurodevelopment and significantly more infrequently diabetes and pancreatic exocrine dysfunction compared to those diagnosed earlier. Conclusions Our results demonstrated improved treatment and long-term outcome in the 21 st century P-CHI patients compared to earlier.

Background: Quality of life (QoL) has not been studied in patients with congenital hyperinsulinism (CHI).Objectives: To examine whether the health-related quality of life (HRQoL) is worsened in patients with persistent or transient CHI.Methods: We studied HRQoL of 65 children with CHI aged 3–17 years (60% males) recruited from the nationwide CHI registry. The median ages were 9.6 (range 3.5–16.3) and 7.4 (3.1–17.9) years in persistent (P-CHI, n = 33) and transient (T-CHI, n = 32) CHI groups, respectively. HRQoL was examined by generic KINDL-R questionnaire and the scores were compared to the age- and gender-specific reference values.Results: In self-reports of subjects aged 11–17 years and in parent reports of children aged 3–17 years, P-CHI or T-CHI children did not have statistically lower scores in any of the six dimensions (physical well-being, emotional well-being, self-esteem, family, friends, and school) or in total scores compared to the reference values.Conclusions: CHI is not associated with low HRQoL in childhood or adolescence.

Background Hyperinsulinism results from inappropriate insulin secretion during hypoglycaemia. Down syndrome is causally linked to a number of endocrine disorders including Type 1 diabetes and neonatal diabetes. We noted a high number of individuals with Down syndrome referred for hyperinsulinism genetic testing, and therefore aimed to investigate whether the prevalence of Down syndrome was increased in our hyperinsulinism cohort compared to the population. Methods We identified individuals with Down syndrome referred for hyperinsulinism genetic testing to the Exeter Genomics Laboratory between 2008 and 2020. We sequenced the known hyperinsulinism genes in all individuals and investigated their clinical features. Results We identified 11 individuals with Down syndrome in a cohort of 2011 patients referred for genetic testing for hyperinsulinism. This represents an increased prevalence compared to the population (2.5/2011 expected vs. 11/2011 observed, p = 6.8 × 10−5). A pathogenic ABCC8 mutation was identified in one of the 11 individuals. Of the remaining 10 individuals, five had non‐genetic risk factors for hyperinsulinism resulting from the Down syndrome phenotype: intrauterine growth restriction, prematurity, gastric/oesophageal surgery, and asparaginase treatment for leukaemia. For five individuals no risk factors for hypoglycaemia were reported although two of these individuals had transient hyperinsulinism and one was lost to follow‐up. Conclusions Down syndrome is more common in patients with hyperinsulinism than in the population. This is likely due to an increased burden of non‐genetic risk factors resulting from the Down syndrome phenotype. Down syndrome should not preclude genetic testing as coincidental monogenic hyperinsulinism and Down syndrome is possible.

Background: Beta-cell monogenic forms of diabetes are the area of diabetes care with the strongest support for a precision medicine approach. We systematically reviewed treatment of hyperglycemia in GCK-related hyperglycemia, HNF1A-diabetes, HNF4A-diabetes, HNF1B-diabetes, Mitochondrial diabetes (MD) due to m.3243A>G variant, 6q24-transient neonatal diabetes (TND) and SLC19A2-diabetes (Thiamine-Responsive Megaloblastic Anemia, TRMA). Methods: Systematic review with data sources from PubMed, MEDLINE and Embase were performed answering specific therapeutic questions for the different subtypes. Individual and group level data was extracted for glycemic outcomes in individuals with genetically confirmed monogenic diabetes. Results: 147 studies met inclusion criteria with only six experimental studies (four randomized trials for HNF1A-diabetes) and the rest being single case reports or cohort studies. Most studies were rated as having moderate or serious risk of bias. For GCK-related hyperglycemia, six studies (35 individuals) showed no deterioration in HbA1c on discontinuing glucose lowering therapy. A randomized trial (n=18 per group) showed that sulfonylureas (SU) were more effective in HNF1A-diabetes than in type 2 diabetes, and cohort and case studies supported SU effectiveness in lowering HbA1c. Two crossover trials (n=15 and n=16) suggested glinides and GLP-1 receptor agonists might be used in place of SU. Evidence for HNF4A-diabetes was limited to three studies (16 individuals) showing lower HbA1c with SU therapy. The 13 studies in HNF1B-diabetes (n=301) and 10 in MD with m.3243A>G variant (n=250) showed that while some patients can be treated with oral agents the majority of patients were insulin treated. In HNF1B-diabetes the attempts to transfer from insulin to oral hypoglycemic agents (OHA) were unsuccessful in most cases. In 6q24-TND there were insufficient studies supporting OHA close to diagnosis before remission but more support for their use after relapse. In SLC19A2-diabetes there was some evidence that treatment with thiamine improved glycemic control and reduced insulin requirement while less than half achieved insulin-independency. Conclusion: There is limited evidence to guide the treatment in monogenic diabetes with most studies being non-randomized and small. The combined data does support: no treatment being needed in GCK-related hyperglycemia; SU being used as the first line treatment in HNF1A-diabetes; SU can be tried in HNF4A-diabetes; insulin often needed in HNF1B-diabetes and MD with the m.3243A>G variant; SU can be tried in 6q24-TND relapse; and thiamine may improve glycemic control in SLC19A2-diabetes. Further evidence, particularly randomized comparative studies, are needed to examine the optimum treatment for glycemic response in all monogenic subtypes.