Diagnosis of congenital Hyperinsulinism can occur not only in infancy but also in later age: a new flow chart from a single center experience

Genetics and Natural History of Non-pancreatectomized Patients With Congenital Hyperinsulinism Due to Variants in ABCC8

CONTEXT

Patients with congenital hyperinsulinism due to ABCC8 variants generally present severe hypoglycemia and those who do not respond to medical treatment typically undergo pancreatectomy. Few data exist on the natural history of non-pancreatectomized patients.

OBJECTIVE

This work aims to describe the genetic characteristics and natural history in a cohort of non-pancreatectomized patients with congenital hyperinsulinism due to variants in the ABCC8 gene.

METHODS

Ambispective study of patients with congenital hyperinsulinism with pathogenic or likely pathogenic variants in ABCC8 treated in the last 48 years and who were not pancreatectomized. Continuous glucose monitoring (CGM) has been periodically performed in all patients since 2003. An oral glucose tolerance test was performed if hyperglycemia was detected in the CGM.

RESULTS

Eighteen non-pancreatectomized patients with ABCC8 variants were included. Seven (38.9%) patients were heterozygous, 8 (44.4%) compound heterozygous, 2 (11.1%) homozygous, and 1 patient carried 2 variants with incomplete familial segregation studies. Seventeen patients were followed up and 12 (70.6%) of them evolved to spontaneous resolution (median age 6.0 ± 4 years; range, 1-14). Five of these 12 patients (41.7%) subsequently progressed to diabetes with insufficient insulin secretion. Evolution to diabetes was more frequent in patients with biallelic variants in the ABCC8 gene.

CONCLUSION

The high remission rate observed in our cohort makes conservative medical treatment a reliable strategy for the management of patients with congenital hyperinsulinism due to ABCC8 variants. In addition, a periodic follow-up of glucose metabolism after remission is recommended, as a significant proportion of patients evolved to impaired glucose tolerance or diabetes (biphasic phenotype).

Clinical and genetic characteristics of patients with congenital hyperinsulinism in 21 non-consanguineous families from Serbia

Persistent hypoglycaemia in newborns and infants is most commonly caused by congenital hyperinsulinism (CHI). Most CHI studies report outcomes in children from both consanguineous and non-consanguineous families which can affect the phenotype-genotype analysis. The aim of this study was to analyze characteristics of patients with CHI in 21 non-consanguineous families from Serbia. This retrospective cohort study included a total of 21 patients with CHI treated in the Mother and Child Healthcare Institute of Serbia during the past 20 years. The prevalence of macrosomia at birth was very low in our cohort (4.8%). Median age at presentation was 6 days, with seizures as the presenting symptom in 76% of patients. Only four patients (19%) were diazoxide unresponsive, and eventually underwent pancreatectomy. Genetic testing was performed in 15 patients and genetic diagnosis was confirmed in 60%, with all patients being heterozygous for detected mutations. The ABCC8 gene mutations were detected in 55.6%, GLUD1 in three patients (33.3%) with HIHA syndrome and one patient had HNF4A gene mutation and unusual prolonged hyperglycaemia lasting 6 days after diazoxide cessation. Neurodevelopmental deficits persisted in 33% of patients.Conclusion: This is the first study regarding CHI patients in Serbia. It suggests that in countries with low consanguinity rate, majority of CHI patients are diazoxide responsive. The most common mutations were heterozygous ABCC8, followed by GLUD1 and HNF4A mutations, suggesting the potential benefit of population-tailored genetic analysis approach, targeting the mutations causing CHI via dominant inheritance model in regions with low consanguinity rates. What is Known: • Persistent hypoglycaemia during infancy and early childhood is most commonly caused by congenital hyperinsulinism (CHI). • Consanguinity is a very important factor regarding the genetics and phenotype of CHI, increasing the risk of autosomal recessive genetic disorders, including the severe, diazoxide-unresponsive forms caused by recessive inactivating mutations in ABCC8 and KCNJ11. What is New: • Results of the present study which included CHI patients from 21 non-consanguineous families suggest that in countries with low consanguinity rates, majority of CHI patients can be diazoxide responsive, with most common mutations being heterozygous ABCC8, followed by GLUD1 and HNF4A mutations. • Unusually prolonged hyperglycaemic reaction to diazoxide treatment in a patient with HNF4A mutation was also described in the present study.

Genotyping of ABCC8, KCNJ11, and HADH in Iranian Infants with Congenital Hyperinsulinism

Background

Congenital hyperinsulinism (CHI) is a heterogeneous disease with various underlying genetic causes. Among different genes considered effective in the development of CHI, ABCC8, KCNJ11, and HADH genes are among the important genes, especially in a population with a considerable rate of consanguineous marriage. Mutational analysis of these genes guides clinicians to better treatment and prediction of prognosis for this rare disease. The present study aimed to evaluate genetic variants in ABCC8, KCNJ11, and HADH genes as causative genes for CHI in the Iranian population.

Methods

The present case series took place in Mashhad, Iran, within 11 years. Every child who had a clinical phenotype and confirmatory biochemical tests of CHI enrolled in this study. Variants in ABCC8, KCNJ11, and HADH genes were analyzed by the polymerase chain reaction and sequencing in our patients.

Results

Among 20 pediatric patients, 16 of them had variants in ABCC8, KCNJ11, and HADH genes. The mean age of genetic diagnosis was 18.6 days. A homozygous missense (c.2041-21G > A) mutation in the ABCC8 gene was seen in three infants. Other common variants were frameshift variants (c.3438dup) in the ABCC8 gene and a missense variant (c.287-288delinsTG) in the KCNJ11 gene. Most of the variants in our population were still categorized as variants of unknown significance and only 7 pathogenic variants were present.

Conclusion

Most variants were located in the ABCC8 gene in our population. Because most of the variants in our population are not previously reported, performing further functional studies is warranted.

An Overview of Hypoglycemia in Children Including a Comprehensive Practical Diagnostic Flowchart for Clinical Use

Hypoglycemia is the result of defects/impairment in glucose homeostasis. The main etiological causes are metabolic and/or endocrine and/or other congenital disorders. Despite hypoglycemia is one of the most common emergencies in neonatal age and childhood, no consensus on the definition and diagnostic work-up exists yet. Aims of this review are to present the current age-related definitions of hypoglycemia in neonatal-pediatric age, to offer a concise and practical overview of its main causes and management and to discuss the current diagnostic-therapeutic approaches. Since a systematic and prompt approach to diagnosis and therapy is essential to prevent hypoglycemic brain injury and long-term neurological complications in children, a comprehensive diagnostic flowchart is also proposed.