What Do We Know about Neonatal Diabetes Caused by PDX1 Mutations?

INTRODUCTION

Neonatal diabetes mellitus (NDM) is characterized by severe hyperglycemia, usually diagnosed in the first few months of an individual's life. It is a genetic disease and one of the main forms of monogenic diabetes. Changes in different genes have already been associated with NDM, including changes in the gene PDX1.

METHODS

In this review, we intend to summarize all neonatal diabetes cases caused by PDX1 mutations reported in the literature. For this purpose, we searched keywords in the literature from PubMed and articles cited by the HGMD database. The search retrieved 84 articles, of which 41 had their full text accessed. After applying the study exclusion criteria, nine articles were included.

RESULTS

Of those articles, we detected thirteen cases of NDM associated with changes in PDX1; the majority in homozygous or compound heterozygous patients. Until now, variants in the PDX1 gene have been a rare cause of NDM; however, few studies have included the screening of this gene in the investigation of neonatal diabetes.

CONCLUSION

In this review, we reinforce the importance of the PDX1 gene inclusion in genetic NGS panels for molecular diagnosis of NDM, and systematic morphological and functional exams of the pancreas when NDM is present.

Paediatric diabetes subtypes in a consanguineous population: a single-centre cohort study from Kurdistan, Iraq

AIMS/HYPOTHESIS

Monogenic diabetes is estimated to account for 1-6% of paediatric diabetes cases in primarily non-consanguineous populations, while the incidence and genetic spectrum in consanguineous regions are insufficiently defined. In this single-centre study we aimed to evaluate diabetes subtypes, obtain the consanguinity rate and study the genetic background of individuals with syndromic and neonatal diabetes in a population with a high rate of consanguinity.

METHODS

Data collection was carried out cross-sectionally in November 2021 at the paediatric diabetic clinic, Dr Jamal Ahmad Rashed Hospital, in Sulaimani, Kurdistan, Iraq. At the time of data collection, 754 individuals with diabetes (381 boys) aged up to 16 years were registered. Relevant participant data was obtained from patient files. Consanguinity status was known in 735 (97.5%) participants. Furthermore, 12 families of children with neonatal diabetes and seven families of children with syndromic diabetes consented to genetic testing by next-generation sequencing. Prioritised variants were evaluated using the American College of Medical Genetics and Genomics guidelines and confirmed by Sanger sequencing.

RESULTS

A total of 269 of 735 participants (36.5%) with known consanguinity status were offspring of consanguineous families. An overwhelming majority of participants (714/754, 94.7%) had clinically defined type 1 diabetes (35% of them were born to consanguineous parents), whereas only eight (1.1%) had type 2 diabetes (38% consanguineous). Fourteen (1.9%) had neonatal diabetes (50% consanguineous), seven (0.9%) had syndromic diabetes (100% consanguineous) and 11 (1.5%) had clinically defined MODY (18% consanguineous). We found that consanguinity was significantly associated with syndromic diabetes (p=0.0023) but not with any other diabetes subtype. The genetic cause was elucidated in ten of 12 participants with neonatal diabetes who consented to genetic testing (homozygous variants in GLIS3 [sibling pair], PTF1A and ZNF808 and heterozygous variants in ABCC8 and INS) and four of seven participants with syndromic diabetes (homozygous variants in INSR, SLC29A3 and WFS1 [sibling pair]). In addition, a participant referred as syndromic diabetes was diagnosed with mucolipidosis gamma and probably has type 2 diabetes.

CONCLUSIONS/INTERPRETATION

This unique single-centre study confirms that, even in a highly consanguineous population, clinically defined type 1 diabetes is the prevailing paediatric diabetes subtype. Furthermore, a pathogenic cause of monogenic diabetes was identified in 83% of tested participants with neonatal diabetes and 57% of participants with syndromic diabetes, with most variants being homozygous. Causative genes in our consanguineous participants were markedly different from genes reported from non-consanguineous populations and also from those reported in other consanguineous populations. To correctly diagnose syndromic diabetes in consanguineous populations, it may be necessary to re-evaluate diagnostic criteria and include additional phenotypic features such as short stature and hepatosplenomegaly.

Not All Diabetic Ketoacidosis in Infant Is Type 1: A Case Report Permanent Neonatal Diabetes

Background/Objective

Neonatal diabetes is a monogenic type of diabetes mellitus. It arises at the first 6 months of age and can be classified as permanent or transient. There are limited cases of neonates with DKA who have heterozygous mutations in INS and PKHD1 genes, especially in Saudi Arabia. We present a case of neonatal diabetes with diabetic ketoacidosis (DKA) born to consanguineous parents in Saudi Arabia. This study aims to highlight the importance of the genetic mutations associated with neonatal diabetes and identify the clinical manifestation features of neonatal diabetes.

Case Report

A six-month-old boy born to consanguineous parents with a family history of neonatal diabetes was diagnosed with DKA. The case was presented to the emergency department (ED) with vomiting and increased urination for 3 days. The child showed signs of severe dehydration and severe metabolic acidosis with a high anion gap and elevated hemoglobin A1C level (16.3%) was reported. According to the genetic test, the patient had an INS and PKHD1gene mutation. The treatment was initiated according to the DKA protocol, and then he received subcutaneous insulin.

Discussion

Neonatal diabetes is a condition caused by several gene mutations. In this case, heterozygous mutations in INS and PKHD1 genes were reported. The type of gene mutation could predict neonatal diabetes type, whether permanent or transient, and its response to treatment.

Conclusion

Genetic testing for neonates soon after birth is suggested for the early detection and classification of neonatal diabetes, especially among children with a family history of neonatal diabetes.

Early-onset diabetes in Africa: A mini-review of the current genetic profile

Early-onset diabetes is poorly diagnosed partly due to its heterogeneity and variable presentations. Although several genes have been associated with the disease, these genes are not well studied in Africa. We sought to identify the major neonatal, early childhood, juvenile, or early-onset diabetes genes in Africa; and evaluate the available molecular methods used for investigating these gene variants. A literature search was conducted on PubMed, Scopus, Africa-Wide Information, and Web of Science databases. The retrieved records were screened and analyzed to identify genetic variants associated with early-onset diabetes. Although 319 records were retrieved, 32 were considered for the current review. Most of these records (22/32) were from North Africa. The disease condition was genetically heterogenous with most cases possessing unique gene variants. We identified 22 genes associated with early-onset diabetes, 9 of which had variants (n = 19) classified as pathogenic or likely pathogenic (PLP). Among the PLP variants, IER3IP1: p.(Leu78Pro) was the variant with the highest number of cases. There was limited data from West Africa, hence the contribution of genetic variability to early-onset diabetes in Africa could not be comprehensively evaluated. It is worth mentioning that most studies were focused on natural products as antidiabetics and only a few studies reported on the genetics of the disease. ABCC8 and KCNJ11 were implicated as major contributors to early-onset diabetes gene networks. Gene ontology analysis of the network associated ion channels, impaired glucose tolerance, and decreased insulin secretions to the disease. Our review highlights 9 genes from which PLP variants have been identified and can be considered for the development of an African diagnostic panel. There is a gap in early-onset diabetes genetic research from sub-Saharan Africa which is much needed to develop a comprehensive, efficient, and cost-effective genetic panel that will be useful in clinical practice on the continent and among the African diasporas.

Incretin hormone responses to carbohydrate and protein/fat are preserved in adults with sulfonylurea-treated KCNJ11 neonatal diabetes

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are thought to be the main drivers of insulin secretion in individuals with sulfonylurea (SU)-treated KCNJ11 permanent neonatal diabetes. The aim of this study was to assess for the first time the incretin hormone response to carbohydrate and protein/fat in adults with sulfonylurea-treated KCNJ11 permanent neonatal diabetes compared with that of controls without diabetes. Participants were given a breakfast high in carbohydrate and an isocaloric breakfast high in protein/fat on two different mornings. Incremental area under the curve and total area under the curve (0-240 minutes) for total GLP-1 and GIP were compared between groups, using non-parametric statistical methods. Post-meal GLP-1 and GIP secretion were similar in cases and controls, suggesting this process is adenosine triphosphate-sensitive potassium channel-independent. Future research will investigate whether treatments targeting the incretin pathway are effective in individuals with KCNJ11 permanent neonatal diabetes who do not have good glycemic control on sulfonylurea alone.

Incomplete penetrance and variable expressivity in monogenic diabetes; a challenge but also an opportunity

Monogenic Forms of Diabetes (MFD) account for about 3% of all diabetes, and their accurate diagnosis often results in life-changing therapeutic reassignment for the patients. Like other Mendelian diseases, reduced penetrance and variable expressivity are often seen in several different types of MFD, where symptoms develop only in a portion of the persons who carry the pathogenic variant or vary widely in symptom severity and age of onset. This complicates diagnosis and disease management in MFD. In addition to its clinical importance, knowledge of genetic modifiers that confer penetrance and expressivity variability opens possibilities to identify protective genetic variants which may help probe the mechanisms of more common forms of diabetes and shed light in new therapeutic strategies. In this review, we will mainly address penetrance and expressivity variation in different types of MFD, factors that confer such variations and opportunities that come with such knowledge. Related literature was searched in PubMed, Medline and Embase. Papers with publication year from 1974 to 2023 are included. Data are either sourced from literatures or from OMIM, Clinvar and 1000 genome browser.

Achievements, prospects and challenges in precision care for monogenic insulin-deficient and insulin-resistant diabetes

Integration of genomic and other data has begun to stratify type 2 diabetes in prognostically meaningful ways, but this has yet to impact on mainstream diabetes practice. The subgroup of diabetes caused by single gene defects thus provides the best example to date of the vision of 'precision diabetes'. Monogenic diabetes may be divided into primary pancreatic beta cell failure, and primary insulin resistance. In both groups, clear examples of genotype-selective responses to therapy have been advanced. The benign trajectory of diabetes due to pathogenic GCK mutations, and the sulfonylurea-hyperresponsiveness conferred by activating KCNJ11 or ABCC8 mutations, or loss-of-function HNF1A or HNF4A mutations, often decisively guide clinical management. In monogenic insulin-resistant diabetes, subcutaneous leptin therapy is beneficial in some severe lipodystrophy. Increasing evidence also supports use of 'obesity therapies' in lipodystrophic people even without obesity. In beta cell diabetes the main challenge is now implementation of the precision diabetes vision at scale. In monogenic insulin-resistant diabetes genotype-specific benefits are proven in far fewer patients to date, although further genotype-targeted therapies are being evaluated. The conceptual paradigm established by the insulin-resistant subgroup with 'adipose failure' may have a wider influence on precision therapy for common type 2 diabetes, however. For all forms of monogenic diabetes, population-wide genome sequencing is currently forcing reappraisal of the importance assigned to pathogenic mutations when gene sequencing is uncoupled from prior suspicion of monogenic diabetes.

Congenital beta cell defects are not associated with markers of islet autoimmunity, even in the context of high genetic risk for type 1 diabetes

AIMS/HYPOTHESIS

A key unanswered question in type 1 diabetes is whether beta cells initiate their own destruction or are victims of an aberrant immune response (beta cell suicide or homicide?). To investigate this, we assessed islet autoantibodies in individuals with congenital beta cell defects causing neonatal diabetes mellitus (NDM).

METHODS

We measured autoantibodies to GAD (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A) in 242 individuals with NDM (median age diagnosed 1.8 months [IQR 0.39-2.9 months]; median age collected 4.6 months [IQR 1.8-27.6 months]; median diabetes duration 2 months [IQR 0.6-23 months]), including 75 whose NDM resulted from severe beta cell endoplasmic reticulum (ER) stress. As a control cohort we also tested samples from 69 diabetes-free individuals (median age collected 9.9 months [IQR 9.0-48.6 months]) for autoantibodies.

RESULTS

We found low prevalence of islet autoantibodies in individuals with monogenic NDM; 13/242 (5.4% [95% CI 2.9, 9.0%]) had detectable GADA, IA-2A and/or ZnT8A. This was similar to the proportion in the control participants who did not have diabetes (1/69 positive [1.4%, 95% CI 0.03, 7.8%], p=0.3). Importantly, monogenic individuals with beta cell ER stress had a similar rate of GADA/IA-2A/ZnT8A positivity to non-ER stress aetiologies (2.7% [95% CI 0.3, 9.3%] vs 6.6% [95% CI 3.3, 11.5%] p=0.4). We observed no association between islet autoimmunity and genetic risk, age at testing (including 30 individuals >10 years at testing) or diabetes duration (p>0.4 for all).

CONCLUSIONS/INTERPRETATION

Our data support the hypothesis that beta cell stress/dysfunction alone does not lead to the production of islet autoantibodies, even in the context of high-risk HLA types. This suggests that additional factors are required to trigger an autoimmune response towards beta cells.

Genetic Heterogeneity and Challenges in the Management of Permanent Neonatal Diabetes Mellitus: A Single-Centre Study from South India

Aim and Objectives

1. To study the clinical outcome, growth and glycaemic control, 2. To study the frequency and type of genetic mutations.

Methods

This is a retrospective study with a review of data of medical records from 2008 till date.

Results

Twelve patients (six males) with neonatal diabetes mellitus (NDM) were identified. Median (interquartile range - (IQR)) age at diagnosis was 72 (31-95) days with a history of consanguinity in 75%. The median birth weight (range) was 2345 (900-3300) g. Follow-up data were available for eight patients with a median age at (IQR) follow-up of 3.3 (3-5.3) years. At follow-up, the mean annual HbA1c was 8.2% at a mean insulin dose of 1.1 U/kg/d. One patient with Wolcott-Rallison syndrome (WRS) and 21α-hydroxylase deficiency had poor growth and intellectual difficulty. The rest demonstrated satisfactory growth with an increase of mean weight centile from 2nd to 13th, height centile from 6.5th to 20th and normal neuro-cognitive development. Eleven patients underwent genetic testing with a molecular diagnosis in 54% (6/11): EIF2AK3 (n = 2) and one each in INS, PDX1, IL2RA and FOXP3. None had variants in ABCC8 or KCNJ11. One with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome underwent haematopoietic stem cell transplant (HSCT) and later succumbed.

Conclusion

Our study demonstrates good clinical outcomes among NDM patients without immune dysfunction. Molecular diagnosis was attained only in around half of the patients (54%) with a great genetic heterogeneity.

Neonatal Diabetes Mellitus: Novel Mutations

OBJECTIVE

To describe the spectrum of neonatal diabetes mellitus (NDM), document new mutations, and review published Indian literature on the etiology of NDM.

METHODS

Retrospective analysis of the clinical and genetic profile of 12 NDM patients.

RESULTS

Eight patients presented with NDM before the age of 6 mo. Three other patients, including 2 siblings presented in later part of infancy. An additional patient was diagnosed at age 5 y with the same etiology as her infant sibling. Four patients had transient diabetes [TNDM:1 each with a mutation in KCNJ11 and INS gene, 2 with ABCC8 mutation], 7 had permanent diabetes [PNDM: 2 siblings with complete glucokinase deficiency, 2 siblings with thiamine responsive megaloblastic anemia (TRMA), 1 with Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX) syndrome and 2 with Wolcott Rallison syndrome, (WRS)]. Four patients had 5 novel mutations. Genetic etiology could not be established in 1 patient with features of insulin resistance. Poorly controlled blood glucose in the TRMA patient led to hyperglycemia-induced hemichorea-hemiballismus, a rare manifestation in children.

CONCLUSIONS

The authors describe 5 novel mutations, in the EIF2AK3, ABCC8, and GCK genes, a homozygous mutation at the ABCC8 locus presenting as TNDM, an obscure phenotype of the GCK gene mutation, and hyperglycemia-induced hemichorea-hemiballismus in a patient with TRMA. In India, PNDM is most commonly due to WRS similar to Middle Eastern countries with high consanguinity rates.

In celebration of a century with insulin - Update of insulin gene mutations in diabetes

Background

While insulin has been central to the pathophysiology and treatment of patients with diabetes for the last 100 years, it has only been since 2007 that genetic variation in the INS gene has been recognised as a major cause of monogenic diabetes. Both dominant and recessive mutations in the INS gene are now recognised as important causes of neonatal diabetes and offer important insights into both the structure and function of insulin. It is also recognised that in rare cases, mutations in the INS gene can be found in patients with diabetes diagnosed outside the first year of life.

Scope of Review

This review examines the genetics and clinical features of monogenic diabetes resulting from INS gene mutations from the first description in 2007 and includes information from 389 patients from 292 families diagnosed in Exeter with INS gene mutations. We discuss the implications for diagnosing and treating this subtype of monogenic diabetes.

Major Conclusions

The dominant mutations in the INS gene typically affect the secondary structure of the insulin protein, usually by disrupting the 3 disulfide bonds in mature insulin. The resulting misfolded protein results in ER stress and beta-cell destruction. In contrast, recessive INS gene mutations typically result in no functional protein being produced due to reduced insulin biosynthesis or loss-of-function mutations in the insulin protein. There are clinical differences between the two genetic aetiologies, between the specific mutations, and within patients with identical mutations.

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Dominant and recessive mutations in the insulin (INS) gene are important causes of neonatal diabetes.

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Associated phenotypes are variable in terms of age at diabetes onset, birth weight and treatment requirements.

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Dominant mutations affect the secondary structure of the insulin protein, resulting in beta-cell ER stress and destruction.

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Recessive mutations result in reduced insulin biosynthesis or loss-of-function mutations of the insulin protein.

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The studies of these forms of diabetes offer important insights into the structure, biosynthesis and secretion of insulin.

Two decades since the fetal insulin hypothesis: what have we learned from genetics?

In 1998 the fetal insulin hypothesis proposed that lower birthweight and adult-onset type 2 diabetes are two phenotypes of the same genotype. Since then, advances in research investigating the role of genetics affecting insulin secretion and action have furthered knowledge of fetal insulin-mediated growth and the biology of type 2 diabetes. In this review, we discuss the historical research context from which the fetal insulin hypothesis originated and consider the position of the hypothesis in light of recent evidence. In summary, there is now ample evidence to support the idea that variants of certain genes which result in impaired pancreatic beta cell function and reduced insulin secretion contribute to both lower birthweight and higher type 2 diabetes risk in later life when inherited by the fetus. There is also evidence to support genetic links between type 2 diabetes secondary to reduced insulin action and lower birthweight but this applies only to loci implicated in body fat distribution and not those influencing insulin resistance via obesity or lipid metabolism by the liver. Finally, we also consider how advances in genetics are being used to explore alternative hypotheses, namely the role of the maternal intrauterine environment, in the relationship between lower birthweight and adult cardiometabolic disease.

Successful Use of a GLP-1 Receptor Agonist as Add-on Therapy to Sulfonylurea in the Treatment of KCNJ11 Neonatal Diabetes

Sulfonylurea monotherapy is the standard treatment for patients with the most common form of permanent neonatal diabetes, KCNJ11 neonatal diabetes, but it is not always sufficient. For the first time, we present a case of successful use of a GLP-1 receptor agonist as add-on therapy in the treatment of a patient with KCNJ11 neonatal diabetes and insufficient effect of sulfonylurea monotherapy. Good glycaemic control was maintained with a HbA1c level of 48 mmol/mol (6.5%) at the end of 26 months' follow-up.

LEARNING POINTS

Genetic testing is important in patients with neonatal diabetes.Sulfonylurea is the standard treatment for patients with the most common mutation (KCNJ11).We present the novel use of a GLP-1 receptor agonist as effective add-on therapy in a patient with KCNJ11 neonatal diabetes and insufficient effect of sulfonylurea monotherapy.

Genotype and Phenotype Heterogeneity in Neonatal Diabetes: A Single Centre Experience in Turkey

OBJECTIVE

Neonatal diabetes mellitus (NDM) may be transient or permanent, and the majority is caused by genetic mutations. Early diagnosis is essential to select the patients who will respond to oral treatment. In this investigation, we aimed to present the phenotype and genotype of our patients with NDM and share our experience in a single tertiary center

METHODS

A total of 16 NDM patients from 12 unrelated families are included in the study. The clinical presentation, age at diagnosis, perinatal and family history, consanguinity, gender, hemoglobin A1c, C-peptide, insulin, insulin autoantibodies, genetic mutations, and response to treatment are retrospectively evaluated.

RESULTS

The median age at diagnosis of diabetes was five months (4 days-18 months) although six patients with a confirmed genetic diagnosis were diagnosed >6 months. Three patients had KCNJ11 mutations, six had ABCC8 mutations, three had EIF2AK3 mutations, and one had a de novo INS mutation. All the permanent NDM patients with KCNJ11 and ABCC8 mutations were started on sulfonylurea treatment resulting in a significant increase in C-peptide level, better glycemic control, and discontinuation of insulin.

CONCLUSION

Although NDM is defined as diabetes diagnosed during the first six months of life, and a diagnosis of type 1 diabetes is more common between the ages of 6 and 24 months, in rare cases NDM may present as late as 12 or even 24 months of age. Molecular diagnosis in NDM is important for planning treatment and predicting prognosis. Therefore, genetic testing is essential in these patients.

Identification of novel compound heterozygous variants in SLC19A2 and the genotype-phenotype associations in thiamine-responsive megaloblastic anemia

BACKGROUND AND AIMS

Thiamine-responsive megaloblastic anemia (TRMA), caused by SLC19A2 loss-of-function variants, is characterized by the triad of megaloblastic anemia, progressive sensorineural deafness, and non-type 1 diabetes mellitus. Here, we present the case of a Chinese infant with two novel variants segregating in compound heterozygous form in SLC19A2 and reviewed genotype-phenotype associations (GPAs) in patients with TRMA.

MATERIALS AND METHODS

Whole-exome sequencing was performed to establish a genetic diagnosis. The clinical manifestations and genetic variants were collected by performing a literature review. The bioinformatics software SIFT, PolyPhen2, and Mutation Taster was applied to predict variant effects and analyze GPAs.

RESULTS

Two novel variants segregating in compound heterozygous form in SLC19A2 (NM_006996.2: exon2:c.336_363del:p.W112fs; exon2:c.358G>T:p.G120X) was identified. Thiamine supplementation corrected anemia and diabetes mellitus but did not improve the hearing defect. In the literature, 183 patients with TRMA with 74 variants in SLC19A2 have been reported, with high incidence in the Middle East, South Asia, and the northern Mediterranean. Patients with biallelic premature termination codon variants presented with more severe phenotypes, and truncating sites on extracellular domains was a protective factor for the hemoglobin level at diagnosis.

CONCLUSION

Two novel compound heterozygous variants (NM_006996.2: exon2:c.336_363del:p.W112fs; exon2:c.358G>T:p.G120X) were identified, and GPAs in TRMA indicated the predictability of clinical manifestations.

Unusual Glycemic Presentations in a Child with a Novel Heterozygous Intragenic INSR Deletion

BACKGROUND

Mutations of the insulin receptor (INSR) gene lead to a wide spectrum of inherited insulin resistance (IR) syndromes. Among these, type A-IR, usually caused by dominant negative INSR mutations, generally presents peri-pubertally in girls.

CASE

A 2.8-year-old girl was referred due to recurrent postprandial and fasting hypoglycemia. She had been born at full-term with birth weight 1.89 kg, and had developed transient neonatal diabetes. Examination showed satisfactory growth, reduced adipose tissue, acanthosis nigricans, and isolated thelarche. After 12 h of fasting, she developed hypoglycemia (glucose 2.8 mmol/L), with inappropriately raised plasma insulin concentration of 5.4 mU/L and suppressed fatty acids and ketone bodies. Oral glucose tolerance testing showed severely increased plasma insulin concentration (>300 mU/L) with hypoglycemia (glucose 1.6 mmol/L) at 2.5 h. She was initially managed on dietary modifications, cornstarch, and then trialed on acarbose for postprandial hyperinsulinemic hypoglycemia (PPHH) with some response. However, she was noted to have increased frequency of hyperglycemia after a couple of years of treatment. She was then switched to metformin and continued to have dietary carbohydrate modification including cornstarch that improved fasting tolerance, hyperglycemia, and postprandial hypoglycemia. Genetic testing identified heterozygous deletion of the last exon of the INSR gene, exon 22.

CONCLUSION

We present a case of type A-IR, caused by a novel INSR deletion, presenting unusually early with transient neonatal diabetes, followed by episodes of hypoglycemia and hyperglycemia during later childhood. Early life presentations, including neonatal diabetes and PPHH, should lead to consideration of type A-IR.

Type 1 diabetes can present before the age of 6 months and is characterised by autoimmunity and rapid loss of beta cells

AIMS/HYPOTHESIS

Diabetes diagnosed at <6 months of age is usually monogenic. However, 10-15% of affected infants do not have a pathogenic variant in one of the 26 known neonatal diabetes genes. We characterised infants diagnosed at <6 months of age without a pathogenic variant to assess whether polygenic type 1 diabetes could arise at early ages.

METHODS

We studied 166 infants diagnosed with type 1 diabetes at <6 months of age in whom pathogenic variants in all 26 known genes had been excluded and compared them with infants with monogenic neonatal diabetes (n = 164) or children with type 1 diabetes diagnosed at 6-24 months of age (n = 152). We assessed the type 1 diabetes genetic risk score (T1D-GRS), islet autoantibodies, C-peptide and clinical features.

RESULTS

We found an excess of infants with high T1D-GRS: 38% (63/166) had a T1D-GRS >95th centile of healthy individuals, whereas 5% (8/166) would be expected if all were monogenic (p < 0.0001). Individuals with a high T1D-GRS had a similar rate of autoantibody positivity to that seen in individuals with type 1 diabetes diagnosed at 6-24 months of age (41% vs 58%, p = 0.2), and had markedly reduced C-peptide levels (median <3 pmol/l within 1 year of diagnosis), reflecting rapid loss of insulin secretion. These individuals also had reduced birthweights (median z score -0.89), which were lowest in those diagnosed with type 1 diabetes at <3 months of age (median z score -1.98).

CONCLUSIONS/INTERPRETATION

We provide strong evidence that type 1 diabetes can present before the age of 6 months based on individuals with this extremely early-onset diabetes subtype having the classic features of childhood type 1 diabetes: high genetic risk, autoimmunity and rapid beta cell loss. The early-onset association with reduced birthweight raises the possibility that for some individuals there was reduced insulin secretion in utero. Comprehensive genetic testing for all neonatal diabetes genes remains essential for all individuals diagnosed with diabetes at <6 months of age. Graphical abstract.

Overview of Atypical Diabetes

Although type 1 diabetes mellitus and, to a lesser extent, type 2 diabetes mellitus, are the prevailing forms of diabetes in youth, atypical forms of diabetes are not uncommon and may require etiology-specific therapies. By some estimates, up to 6.5% of children with diabetes have monogenic forms. Mitochondrial diabetes and cystic fibrosis related diabetes are less common but often noted in the underlying disease. Atypical diabetes should be considered in patients with a known disorder associated with diabetes, aged less than 25 years with nonautoimmune diabetes and without typical characteristics of type 2 diabetes mellitus, and/or with comorbidities associated with atypical diabetes.

Transcription factors that shape the mammalian pancreas

Improving our understanding of mammalian pancreas development is crucial for the development of more effective cellular therapies for diabetes. Most of what we know about mammalian pancreas development stems from mouse genetics. We have learnt that a unique set of transcription factors controls endocrine and exocrine cell differentiation. Transgenic mouse models have been instrumental in studying the function of these transcription factors. Mouse and human pancreas development are very similar in many respects, but the devil is in the detail. To unravel human pancreas development in greater detail, in vitro cellular models (including directed differentiation of stem cells, human beta cell lines and human pancreatic organoids) are used; however, in vivo validation of these results is still needed. The current best 'model' for studying human pancreas development are individuals with monogenic forms of diabetes. In this review, we discuss mammalian pancreas development, highlight some discrepancies between mouse and human, and discuss selected transcription factors that, when mutated, cause permanent neonatal diabetes. Graphical abstract.

Diabetes management in Wolcott-Rallison syndrome: analysis from the German/Austrian DPV database

Background

Wolcott-Rallison syndrome (WRS) is characterized by permanent early-onset diabetes, skeletal dysplasia and several additional features, e.g. recurrent liver failure. This is the first multicentre approach that focuses on diabetes management in WRS. We searched the German/Austrian Diabetes-Patienten-Verlaufsdokumentation (DPV) registry and studied anthropometric characteristics, diabetes treatment, glycaemic control and occurrence of severe hypoglycaemia (SH) and diabetic ketoacidosis (DKA) in 11 patients with WRS. Furthermore, all local treatment centres were personally contacted to retrieve additional information on genetic characteristics, migration background and rate of consanguinity.

Results

Data were analysed at diabetes onset and after a median follow-up period of 3 (1.5–9.0) years (time from diagnosis to latest follow-up). Median age at diabetes onset was 0.2 (0.1–0.3) years, while onset was delayed in one patient (aged 16 months). Seventy percent of patients manifested with DKA. At follow-up, 90% of patients were on insulin pump therapy requiring 0.7 [0.5–1.0] IU of insulin/kg/d. More than two third of patients had HbA1c level ≥ 8%, 40% experienced at least one episode of SH in the course of the disease. Three patients died at 0.6, 5 and 9 years of age, respectively. To the best of our knowledge three patients carried novel mutations in EIF2AK3.

Conclusion

Insulin requirements of individuals with WRS registered in DPV appear to be comparable to those of preschool children with well-controlled type 1 diabetes, while glycaemic control tends to be worse and episodes of SH tend to be more common. The majority of individuals with WRS in the DPV registry does not reach glycaemic target for HbA1c as defined for preschool children (< 7.5%). International multicentre studies are required to further improve our knowledge on the care of children with WRS.

Neonatal diabetes caused by the heterozygous Pro1198Leu mutation in the ABCC8 gene in a male infant: 6-year clinical course

Neonatal diabetes is a rare disease, often caused by a monogenic abnormality. A male infant patient developed diabetic ketoacidosis at 2 months-of-age due to the heterozygous ABCC8 gene mutation (p.Pro1198Leu). After genetic diagnosis, insulin therapy was successfully transitioned to oral sulfonylurea therapy. For >6 years, oral sulfonylurea therapy has been safe and effective, and the required amount of sulfonylureas has progressively decreased. The mutation was transmitted in an autosomal-dominant fashion across three generations of his family, but the severity of diabetes varied among members from neonatal diabetes to mild diabetes. One family member had normal glucose tolerance despite having the mutation. This case presentation could help in the understanding of neonatal diabetes caused by the ABCC8 gene mutation.

Non classic presentations of a genetic mutation typically associated with transient neonatal diabetes

SUMMARY

This case report describes a family pedigree of a mother and her children with an E227K mutation in the KCNJ11 gene. People with this particular gene mutation typically present with transient neonatal diabetes; with more than half the cohort relapsing into permanent diabetes in adolescence or early adulthood. However, the mother developed diabetes as an adolescent and thus was initially diagnosed as having Type 1 Diabetes. All her children have inherited the same genetic mutation but with differing presentations. Her second, third and fourth child presented with transient neonatal diabetes which remitted at varying times. Her first child is 16 years old but had not developed diabetes at the time of writing. The KCNJ11 gene codes for the KIR6.2 subunit of the KATP channels of the pancreatic beta cells. Mutations in this gene limit insulin release from beta cells despite high blood glucose concentrations. Most people with diabetes caused by this genetic mutation can be successfully managed with glibenclamide. Learning of the genetic mutation changed the therapeutic approach to the mother's diabetes and enabled rapid diagnosis for her children. Through this family, we identified that an identical genetic mutation does not necessarily lead to the same diabetic phenotype. We recommend clinicians to consider screening for this gene in their patients whom MODY is suspected; especially in those presenting before the age of 25 who remain C-peptide positive.

LEARNING POINTS

KATP channel closure in pancreatic beta cells is a critical step in stimulating insulin release. Mutations in the KIR6.2 subunit can result in the KATP channels remaining open, limiting insulin release. People with KCNJ11 mutations may not present with neonatal diabetes as the age of presentation of diabetes can be highly variable. Most affected individuals can be treated successfully with glibenclamide, which closes the KATP channels via an independent mechanism. All first degree relatives of the index case should be offered genetic testing, including asymptomatic individuals. Offspring of affected individuals should be monitored for neonatal diabetes from birth. Affected individuals will require long-term follow-up as there is a high risk of recurrence in later life.

Diagnostic Genetic Testing for Monogenic Diabetes and Congenital Hyperinsulinemia

Monogenic diabetes and hyperinsulinism are genetically heterogeneous disorders. The determination of the genetic etiology defines the diagnostic subtype, predicts prognosis, and importantly can guide clinical management. This chapter focuses on the processes and methodologies utilized in the diagnostic testing for monogenic diabetes and congenital hyperinsulinism (i.e., Sanger sequencing and targeted next-generation sequencing).

Diagnosis and management of neonatal diabetes mellitus: A survey of physicians' perceptions and practices in ASPED countries

AIM

To ascertain the awareness and practice of neonatal diabetes mellitus (NDM) among paediatricians in Arab countries.

METHODS

An online questionnaire was distributed to physicians associated with the Arab Society for Paediatric Endocrinology and Diabetes (ASPED).

RESULTS

We received 126 replies, from 16 countries. All except one classified the survey's case scenario as NDM and 94% agreed that NDM patients should have detailed assessment to identify extra-pancreatic features. Although 92% felt that genetic testing is necessary, only 72% requesting them routinely and 32% unaware of the availability of free genetic testing. Insulin is considered the initial therapy for 93% and 80% diluted insulin to deliver accurate doses. Basal-bolus regimen was preferred by 36% and similar percentage used insulin pump. The remaining 28% favour long acting insulin alone. Oral sulfonylureas would be tried empirically by 34% and 69% would do so if genetic testing is unavailable. Whilst 70% have no local NDM management guidelines, 41% are unaware of any international guidelines.

CONCLUSIONS

The ASPED surveyed clinicians have good awareness of NDM diagnosis with marked variation in their practice raising the need to establish management guideline for the condition. The survey highlights areas to focus on in developing consensus and educational activities.

Clinical Characteristics, Molecular Features, and Long-Term Follow-Up of 15 Patients with Neonatal Diabetes: A Single-Centre Experience

BACKGROUND

Diabetes diagnosed within the first 6 months of life is defined as neonatal diabetes mellitus (NDM). Mutations in the KCNJ11, ABCC8, and INS genes are the most common cause of permanent NDM. In populations with a high rate of consanguinity, Wolcott-Rallison syndrome caused by biallelic EIF2AK3 mutations is common.

METHODS

We studied the clinical characteristics and underlying genetic cause of disease in 15 individuals with diabetes onset before 6 months of age as defined by sustained hyperglycaemia requiring insulin treatment. Patients who had a remission of the diabetes, defined by a normal blood glucose and HbA1c value without insulin or sulphonylurea (SU) treatment, within the first 18 months of life were classified as having transient NDM (TNDM).

RESULTS

We report 15 patients with NDM from 14 unrelated families, including 10 with reported parental consanguinity. 1/15 patients had a remission of diabetes, leading to a diagnosis of TNDM. Mutations were detected in 80% (n = 12/15) of the cohort (ABCC8 [n = 4], PTF1A-distal enhancer [n = 3], KCNJ11 [n = 2], EIF2AK3 [n = 1], INS [n = 1], and SLC19A2 [n = 1]). All cases were initially treated with multiple dose insulin injections. One patient with an ABCC8 mutation transitioned from insulin to SU resulting in improved metabolic control at the age of 20 years.

CONCLUSION

Although the number of individuals born to consanguineous parents was considerably high in this cohort, KATP channel mutations (ABCC8/KCNJ11) were more common than EIF2AK3 mutations (n = 6 vs. n = 1). Genetic analyses should be performed in all NDM cases due to the potential impact on treatment and prognosis.

Precision Medicine: Long-Term Treatment with Sulfonylureas in Patients with Neonatal Diabetes Due to KCNJ11 Mutations

PURPOSE OF REVIEW

The goal of this review is to provide updates on the safety and efficacy of long-term sulfonylurea use in patients with KCNJ11-related diabetes. Publications from 2004 to the present were reviewed with an emphasis on literature since 2014.

RECENT FINDINGS

Sulfonylureas, often taken at high doses, have now been utilized effectively in KCNJ11 patients for over 10 years. Mild-moderate hypoglycemia can occur, but in two studies with a combined 975 patient-years on sulfonylureas, no severe hypoglycemic events were reported. Improvements in neurodevelopment and motor function after transition to sulfonylureas continue to be described. Sulfonylureas continue to be an effective, sustainable, and safe treatment for KCNJ11-related diabetes. Ongoing follow-up of patients in research registries will allow for deeper understanding of the facilitators and barriers to long-term sustainability. Further understanding of the effect of sulfonylurea on long-term neurodevelopmental outcomes, and the potential for adjunctive therapies, is needed.

Familial GATA6 mutation causing variably expressed diabetes mellitus and cardiac and renal abnormalities

A 26-year-old man presented with a combination of permanent neonatal diabetes due to pancreatic aplasia, complex congenital heart disease, central hypogonadism and growth hormone deficiency, structural renal abnormalities with proteinuria, umbilical hernia, neurocognitive impairment and dysmorphic features. His older brother had diabetes mellitus due to pancreatic hypoplasia, complex congenital heart disease, hypospadias and umbilical hernia. Their father had an atrial septal defect, umbilical hernia and diabetes mellitus diagnosed incidentally in adulthood on employment screening. The proband's paternal grandmother had a congenital heart defect. Genetic testing of the proband revealed a novel heterozygous missense variant (Chr18:g.19761441T>C, c.1330T>C, p.Cys444Arg) in exon 4 of GATA6, which is class 5 (pathogenic) using American College of Medical Genetics and Genomics guidelines and is likely to account for his multisystem disorder. The same variant was detected in his brother and father, but not his paternal grandmother. This novel variant of GATA6 likely occurred de novo in the father with autosomal dominant inheritance in the proband and his brother. The case is exceptional as very few families with monogenic diabetes due to GATA6 mutations have been reported to date and we describe a new link between GATA6 and renal pathology. Learning points: Monogenic diabetes should be suspected in patients presenting with syndromic features, multisystem congenital disease, neonatal-onset diabetes and/or a suggestive family history. Recognition and identification of genetic diabetes may improve patient understanding and empowerment and allow for better tailored management. Identification of a genetic disorder may have important implications for family planning.

EIF2AK3 novel mutation in a child with early-onset diabetes mellitus, a case report

Background

Wolcott-Rallison syndrome (WRS) is caused by a biallelic mutation in the gene encoding eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3) on chromosome 2p11.2. This condition is characterized by permanent early-onset diabetes mellitus, epiphyseal dysplasia, and hepatic dysfunction. We report a patient with WRS born to a consanguineous marriage due to a novel biallelic frameshift mutation in the EIF2AK3 gene.

Case presentation

Our patient was a 2-year-and-6-month-old Yemeni girl born to consanguineous parents who was diagnosed with neonatal diabetes at 20 days of age. She presented with chronic diarrhea and liver dysfunction. The child was normocephalic and exhibited failure to thrive and hepatomegaly with no skeletal deformities. Further investigations revealed microcytic anemia, liver impairment and primary hypothyroidism. Genetic testing confirmed the diagnosis of WRS via identification of a novel biallelic frameshift mutation in the EIF2AK3 gene. During her hospital stay, she went into septic shock and developed multi-organ failure, including fulminant hepatic failure. She unfortunately died within 2 weeks of her hospital stay.

Conclusions

Wolcott-Rallison syndrome is recognized as the most common cause of early-onset diabetes in infants born to consanguineous marriages. Screening for genetic mutations in EIF2AK3 is recommended for establishing early diagnosis, providing genetic counselling, and predicting the development of additional clinical features, most importantly hepatic failure. Hence, this screening is important for guiding optimal management and improving patient outcome.

Electronic supplementary material

The online version of this article (10.1186/s12887-019-1432-8) contains supplementary material, which is available to authorized users.

Precision Diabetes Is Slowly Becoming a Reality

The concept of precision medicine is becoming increasingly popular. The use of big data, genomics and other "omics" like metabolomics, proteomics and transcriptomics could make the dream of personalised medicine become a reality in the near future. As far as polygenic forms of diabetes like type 2 and type 1 diabetes are concerned, interesting leads are emerging, but precision diabetes is still in its infancy. However, with regard to monogenic forms of diabetes like maturity-onset diabetes of the young and neonatal diabetes mellitus, rapid strides have been made and precision diabetes has already become part of the clinical tools used at advanced diabetes centres. In patients with some monogenic form of diabetes, if the appropriate gene defects are identified, insulin injections can be stopped and be replaced by oral sulphonylurea drugs. In the coming years, rapid advances can be expected in the field of precision diabetes, thereby making the control of diabetes more effective and hopefully leading to prevention of its complications and improvement of the quality of life of people afflicted with diabetes.

Mutations in glucokinase and other genes detected in neonatal and type 1B diabetes patient using whole exome sequencing may lead to disease-causing changes in protein activity

Monogenic diabetes is caused by mutations that reduce β-cell function. While Sanger sequencing is the standard method used to detect mutated genes. Next-generation sequencing techniques, such as whole exome sequencing (WES), can be used to find multiple gene mutations in one assay. We used WES to detect genetic mutations in both permanent neonatal (PND) and type 1B diabetes (T1BD). A total of five PND and nine T1BD patients were enrolled in this study. WES variants were assessed using VarioWatch, excluding those identified previously. Sanger sequencing was used to confirm the mutations, and their pathogenicity was established via the literature or bioinformatic/functional analysis. The PND and T1BD patients were diagnosed at 0.1-0.5 and 0.8-2.7 years of age, respectively. Diabetic ketoacidosis was present at diagnosis in 60% of PND patients and 44.4% of T1BD patients. We found five novel mutations in five different genes. Notably, patient 602 had a novel homozygous missense mutation c.1295C > A (T432 K) in the glucokinase (GCK) gene. Compared to the wild-type recombinant protein, the mutant protein had significantly lower enzymatic activity (2.5%, p = 0.0002) and V_max (1.23 ± 0.019 vs. 0.33 ± 0.016, respectively; p = 0.005). WES is a robust technique that can be used to unravel the etiologies of genetically heterogeneous forms of diabetes. Homozygous inactivating mutations of the GCK gene may have a significant role in PND pathogenesis.

Genetics of Monogenic Diabetes: Present Clinical Challenges

PURPOSE OF REVIEW

Monogenic forms of diabetes have specific treatments that differ from the standard care provided for type 1 and type 2 diabetes, making the appropriate diagnosis essential. In this review, we discuss current clinical challenges that remain, including improving case-finding strategies, particularly those that have transethnic applicability, and understanding the interpretation of genetic variants as pathogenic, with clinically meaningful impacts.

RECENT FINDINGS

Biomarker approaches to the stratification for genetic testing now appear to be most effective in identifying cases of monogenic diabetes, and use of genetic risk scores may also prove useful. However, applicability in all ethnic groups is lacking. Challenges remain in the classification of genes as diabetes-causing and the interpretation of genetic variants at the clinical interface. Since the discovery that genetic defects can cause neonatal or young-onset diabetes, multiple causal genes have been identified and there have been many advances in strategies to detect genetic forms of diabetes and their treatments. Approaches learnt from monogenic diabetes are now being translated to polygenic diabetes.

Heterogeneous nature of diabetes in a family with a gain-of-function mutation in the ATP-binding cassette subfamily C member 8 (ABCC8) gene

Gain-of-function ATP-binding cassette subfamily C member 8 (ABCC8) mutations are known to cause neonatal diabetes mellitus and maturity-onset diabetes in the young. However, the intrafamilial heterogeneous nature of diabetes caused by the ABCC8 mutation is not fully understood to date. To clarify the intrafamilial heterogeneous nature of monogenetic diabetes, we conducted a case study on a family with ABCC8 mutations. We investigated eight family members, including a neonatal diabetes patient, based on metabolic features and genetic analysis. All coding exons and exon-intron boundaries of the KCNJ11, ABCC8, GCK, HNF1A, and HNF4A genes were amplified from genomic DNA and directly sequenced. Five gene mutation carriers with ABCC8 (c.1819G>A/p.V607M) were identified in this family, and the onset and severity of diabetes progressively worsened across the three generations. Each of the ABCC8 gene mutation carrier family members were diagnosed with diabetes as follows: the grandfather with type 2 diabetes at 35 years of age, the aunt with slowly-progressive insulin-dependent diabetes at 18 years of age, the mother with ketosis-onset insulin-dependent diabetes at 14 years of age, the sister with impaired glucose tolerance at 9 years of age, and the proband with transient neonatal diabetes at birth. The present study shows the heterogeneous nature of diabetes in a family with a gain-of-function mutation in the ABCC8 gene.

Congenital Diabetes: Comprehensive Genetic Testing Allows for Improved Diagnosis and Treatment of Diabetes and Other Associated Features

PURPOSE OF REVIEW

The goal of this review is to provide updates on congenital (neonatal) diabetes from 2011 to present, with an emphasis on publications from 2015 to present.

RECENT FINDINGS

There has been continued worldwide progress in uncovering the genetic causes of diabetes presenting within the first year of life, including the recognition of nine new causes since 2011. Management has continued to be refined based on underlying molecular cause, and longer-term experience has provided better understanding of the effectiveness, safety, and sustainability of treatment. Associated conditions have been further clarified, such as neurodevelopmental delays and pancreatic insufficiency, including a better appreciation for how these "secondary" conditions impact quality of life for patients and their families. While continued research is essential to understand all forms of congenital diabetes, these cases remain a compelling example of personalized genetic medicine.

A Novel KCNJ11 Mutation Associated with Transient Neonatal Diabetes

Neonatal diabetes mellitus (NDM) is a rare type of monogenic diabetes that presents in the first 6 months of life. Activating mutations in the KCNJ11 gene encoding for the Kir6.2 subunit of the ATP-sensitive potassium (K_ATP ) channel can lead to transient NDM (TNDM) or to permanent NDM (PNDM). A female infant presented on the 22^nd day of life with severe hyperglycemia and ketoacidosis (glucose: 907mg/dL, blood gas pH: 6.84, HCO₃: 6 mmol/L). She was initially managed with intravenous (IV) fluids and IV insulin. Ketoacidosis resolved within 48 hours and she was started on subcutaneous insulin injections with intermediate acting insulin NPH twice daily requiring initially 0.75-1.35 IU/kg/d. Pre-prandial C-peptide levels were 0.51 ng/mL (normal: 1.77-4.68). Insulin requirements were gradually reduced and insulin administration was discontinued at the age of 10 months with subsequent normal glucose and HbA1c levels. C-peptide levels normalized (pre-prandial: 1.6 ng/mL, postprandial: 2 ng/mL). Genetic analysis identified a novel missense mutation (p.Pro254Gln) in the KCNJ11 gene. We report a novel KCNJ11 mutation in a patient who presented in the first month of life with a phenotype of NDM that subsided at the age of 10 months. It is likely that the novel p.P254Q mutation results in mild impairment of the K_ATP channel function leading to TNDM.

Neonatal Diabetes: Two Cases with Isolated Pancreas Agenesis due to Homozygous PTF1A Enhancer Mutations and One with Developmental Delay, Epilepsy, and Neonatal Diabetes Syndrome due to KCNJ11 Mutation

Neonatal diabetes mellitus is a rare form of monogenic diabetes which is diagnosed in the first six months of life. Here we report three patients with neonatal diabetes; two with isolated pancreas agenesis due to mutations in the pancreas-specific transcription factor 1A (PTF1A) enhancer and one with developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, due to a KCNJ11 mutation. The two cases with mutations in the distal enhancer of PTF1A had a homozygous g.23508363A>G and a homozygous g.23508437A>G mutation respectively. Previous functional analyses showed that these mutations can decrease expression of PTF1A which is involved in pancreas development. Both patients were born small for gestational age to consanguineous parents. Both were treated with insulin and pancreatic enzymes. One of these patients’ fathers was also homozygous for the PTF1A mutation, whilst his partner and the parents of the other patient were heterozygous carriers. In the case with DEND sydrome, a previosly reported heterozygous KCNJ11 mutation, p.Cys166Tyr (c.497G>A), was identified. This patient was born to nonconsanguineous parents with normal birth weight. The majority of neonatal diabetes patients with KCNJ11 mutations will respond to sulphonylurea treatment. Therefore Glibenclamide, an oral antidiabetic of the sulphonylurea group, was started. This treatment regimen relatively improved blood glucose levels and neurological symptoms in the short term. Because we could not follow the patient in the long term, we are not able to draw conclusions about the efficacy of the treatment. Although neonatal diabetes mellitus can be diagnosed clinically, genetic analysis is important since it is a guide for the treatment and for prognosis.

Transient Neonatal Diabetes due to a Mutation in KCNJ11 in a Child with Klinefelter Syndrome

Klinefelter syndrome is the most frequent chromosomal aneuploidy in males occurring in about 1 in 660 males. Epidemiological studies have demonstrated increased risk of type 1 diabetes and type 2 diabetes in adults with Klinefelter syndrome. There is only one previous report of neonatal diabetes in a patient with Klinefelter syndrome. We report transient neonatal diabetes due to a pathogenic heterozygous variant in KCNJ11 in a male infant with Klinefelter syndrome. A 78-day old male infant was noted to have sustained hyperglycemia with serum glucose ranging between 148 mg/dL (8.2 mmol/L) and 381 mg/dL (21.2 mmol/L) three days after undergoing a complete repair of an atrioventricular defect. Hemoglobin A1c was 6.6%. The patient was born at term with a birth weight of 2.16 kg following a pregnancy complicated by gestational diabetes that was controlled with diet. The patient was initially started on a continuous intravenous insulin drip and subsequently placed on subcutaneous insulin (glargine, human isophane and regular insulin). Insulin was gradually decreased and eventually discontinued at seven months of age. Chromosomal microarray at 11 weeks of age showed XXY and a panel-based, molecular test for neonatal diabetes revealed a pathogenic heterozygous variant c.685G>A (p.Glu229Lys) in KCNJ11. The patient is now 34 months old and continues to have normal fasting and post-prandial glucose and HbA1C levels. The patient will need prospective follow up for assessment of his glycemic status. To our knowledge this is the second reported case of neonatal diabetes in an infant with Klinefelter syndrome and the first due to a mutation in the KCNJ11 in a patient with Klinefelter syndrome.

Neonatal Diabetes Mellitus: An Update on Diagnosis and Management

Neonatal diabetes mellitus is likely to be due to an underlying monogenic defect when it occurs at less than 6 months of age. Early recognition and urgent genetic testing are important for predicting the clinical course and raising awareness of possible additional features. Early treatment of sulfonylurea-responsive types of neonatal diabetes may improve neurologic outcomes. It is important to distinguish neonatal diabetes mellitus from other causes of hyperglycemia in newborns. Other causes include infection, stress, inadequate pancreatic insulin production in preterm infants, among others. This review explores the diagnostic approach, mutation types, management, and clinical course of neonatal diabetes.

Methods for Characterizing Disease-Associated ATP-Sensitive Potassium Channel Mutations

The ATP-sensitive potassium (K_ATP) channel formed by the inwardly rectifying potassium channel Kir6.2 and the sulfonylurea receptor 1 (SUR1) plays a key role in regulating insulin secretion. Genetic mutations in KCNJ11 or ABCC8 which encode Kir6.2 and SUR1 respectively are major causes of insulin secretion disorders: those causing loss of channel function lead to congenital hyperinsulinism, whereas those causing gain of channel function result in neonatal diabetes and in some cases developmental delay, epilepsy, and neonatal diabetes, referred to as the DEND syndrome. Understanding how disease mutations disrupt channel expression and function is important for disease diagnosis and for devising effective therapeutic strategies. Here, we describe a workflow including several biochemical and functional assays to assess the effects of mutations on channel expression and function.

Screening for neonatal diabetes at day 5 of life using dried blood spot glucose measurement

AIMS/HYPOTHESIS

The majority of infants with neonatal diabetes mellitus present with severe ketoacidosis at a median of 6 weeks. The treatment is very challenging and can result in severe neurological sequelae or death. The genetic defects that cause neonatal diabetes are present from birth. We aimed to assess if neonatal diabetes could be diagnosed earlier by measuring glucose in a dried blood spot collected on day 5 of life.

METHODS

In this retrospective case-control study we retrieved blood spot cards from 11 infants with genetically confirmed neonatal diabetes (median age of diagnosis 6 [range 2-112] days). For each case we also obtained one (n = 5) or two (n = 6) control blood spot cards collected on the same day. Glucose was measured on case and control blood spot cards. We established a normal range for random glucose at day 5 of life in 687 non-diabetic neonates.

RESULTS

All 11 neonates with diabetes had hyperglycaemia present on day 5 of life, with blood glucose levels ranging from 10.2 mmol/l to >30 mmol/l (normal range 3.2-6.0 mmol/l). In six of these neonates the diagnosis of diabetes was made after screening at day 5, with the latest diagnosis made at 16 weeks.

CONCLUSIONS/INTERPRETATION

Neonatal diabetes can be detected on day 5 of life, preceding conventional diagnosis in most cases. Earlier diagnosis by systematic screening could lead to prompt genetic diagnosis and targeted treatment, thereby avoiding the most severe sequelae of hyperglycaemia in neonates.

An ABCC8 Nonsense Mutation Causing Neonatal Diabetes Through Altered Transcript Expression

The pancreatic ATP-sensitive K+ (K-ATP) channel is a key regulator of insulin secretion. Gain-of-function mutations in the genes encoding the Kir6.2 (KCNJ11) and SUR1 (ABCC8) subunits of the channel cause neonatal diabetes, whilst loss-of-function mutations in these genes result in congenital hyperinsulinism. We report two patients with neonatal diabetes in whom we unexpectedly identified recessively inherited loss-of-function mutations. The aim of this study was to investigate how a homozygous nonsense mutation in ABCC8 could result in neonatal diabetes. The ABCC8 p.Glu747* was identified in two unrelated Vietnamese patients. This mutation is located within the in-frame exon 17 and RNA studies confirmed (a) the absence of full length SUR1 mRNA and (b) the presence of the alternatively spliced transcript lacking exon 17. Successful transfer of both patients to sulphonylurea treatment suggests that the altered transcript expression enhances the sensitivity of the K-ATP channel to Mg-ADP/ATP. This is the first report of an ABCC8 nonsense mutation causing a gain-of-channel function and these findings extend the spectrum of K-ATP channel mutations observed in patients with neonatal diabetes.

A successful transition to sulfonylurea treatment in male infant with neonatal diabetes caused by the novel abcc8 gene mutation and three years follow-up

Neonatal diabetes mellitus is a rare monogenic disease with incidence of 1/90,000 newborns. A case of two months aged male infant with life threatening diabetic ketoacidosis is presented with novel ABCC8 gene mutation (p.F577L), successful transition from insulin to sulfonylurea and follow-up of three years.

Precision diabetes: learning from monogenic diabetes

The precision medicine approach of tailoring treatment to the individual characteristics of each patient or subgroup has been a great success in monogenic diabetes subtypes, MODY and neonatal diabetes. This review examines what has led to the success of a precision medicine approach in monogenic diabetes (precision diabetes) and outlines possible implications for type 2 diabetes. For monogenic diabetes, the molecular genetics can define discrete aetiological subtypes that have profound implications on diabetes treatment and can predict future development of associated clinical features, allowing early preventative or supportive treatment. In contrast, type 2 diabetes has overlapping polygenic susceptibility and underlying aetiologies, making it difficult to define discrete clinical subtypes with a dramatic implication for treatment. The implementation of precision medicine in neonatal diabetes was simple and rapid as it was based on single clinical criteria (diagnosed <6 months of age). In contrast, in MODY it was more complex and slow because of the lack of single criteria to identify patients, but it was greatly assisted by the development of a diagnostic probability calculator and associated smartphone app. Experience in monogenic diabetes suggests that successful adoption of a precision diabetes approach in type 2 diabetes will require simple, quick, easily accessible stratification that is based on a combination of routine clinical data, rather than relying on newer technologies. Analysing existing clinical data from routine clinical practice and trials may provide early success for precision medicine in type 2 diabetes.

First case of neonatal diabetes with KCNJ11 Q52R mutation successfully switched from insulin to sulphonylurea treatment

In this report, we present the first known case of intermediate developmental delay, epilepsy and permanent neonatal diabetes (DEND) syndrome caused by a Q52R mutation in the KCNJ11 gene who was successfully switched (at age 1.3 years) to sulphonylurea monotherapy, namely glibenclamide. The most recent evaluation, after 2 years, showed a glycated hemoglobin level of 6.0% (42 mmol/mol). This mutation is so severe that none of the previously reported four cases were able to switch from insulin to sulphonylurea monotherapy. The Q52R mutation seems to have a chance of positive response to glibenclamide administered every 3–6 h instead of the classical 8–12 h, in doses around or above 2.5 mg/kg/day.

Neonatal diabetes caused by a homozygous KCNJ11 mutation demonstrates that tiny changes in ATP sensitivity markedly affect diabetes risk

AIMS/HYPOTHESIS

The pancreatic ATP-sensitive potassium (KATP) channel plays a pivotal role in linking beta cell metabolism to insulin secretion. Mutations in KATP channel genes can result in hypo- or hypersecretion of insulin, as in neonatal diabetes mellitus and congenital hyperinsulinism, respectively. To date, all patients affected by neonatal diabetes due to a mutation in the pore-forming subunit of the channel (Kir6.2, KCNJ11) are heterozygous for the mutation. Here, we report the first clinical case of neonatal diabetes caused by a homozygous KCNJ11 mutation.

METHODS

A male patient was diagnosed with diabetes shortly after birth. At 5 months of age, genetic testing revealed he carried a homozygous KCNJ11 mutation, G324R, (Kir6.2-G324R) and he was successfully transferred to sulfonylurea therapy (0.2 mg kg(-1) day(-1)). Neither heterozygous parent was affected. Functional properties of wild-type, heterozygous and homozygous mutant KATP channels were examined after heterologous expression in Xenopus oocytes.

RESULTS

Functional studies indicated that the Kir6.2-G324R mutation reduces the channel ATP sensitivity but that the difference in ATP inhibition between homozygous and heterozygous channels is remarkably small. Nevertheless, the homozygous patient developed neonatal diabetes, whereas the heterozygous parents were, and remain, unaffected. Kir6.2-G324R channels were fully shut by the sulfonylurea tolbutamide, which explains why the patient's diabetes was well controlled by sulfonylurea therapy.

CONCLUSIONS/INTERPRETATION

The data demonstrate that tiny changes in KATP channel activity can alter beta cell electrical activity and insulin secretion sufficiently to cause diabetes. They also aid our understanding of how the Kir6.2-E23K variant predisposes to type 2 diabetes.

Successful transfer to sulfonylureas in KCNJ11 neonatal diabetes is determined by the mutation and duration of diabetes

AIMS/HYPOTHESIS

The finding that patients with diabetes due to potassium channel mutations can transfer from insulin to sulfonylureas has revolutionised the management of patients with permanent neonatal diabetes. The extent to which the in vitro characteristics of the mutation can predict a successful transfer is not known. Our aim was to identify factors associated with successful transfer from insulin to sulfonylureas in patients with permanent neonatal diabetes due to mutations in KCNJ11 (which encodes the inwardly rectifying potassium channel Kir6.2).

METHODS

We retrospectively analysed clinical data on 127 patients with neonatal diabetes due to KCNJ11 mutations who attempted to transfer to sulfonylureas. We considered transfer successful when patients completely discontinued insulin whilst on sulfonylureas. All unsuccessful transfers received ≥0.8 mg kg(-1) day(-1) glibenclamide (or the equivalent) for >4 weeks. The in vitro response of mutant Kir6.2/SUR1 channels to tolbutamide was assessed in Xenopus oocytes. For some specific mutations, not all individuals carrying the mutation were able to transfer successfully; we therefore investigated which clinical features could predict a successful transfer.

RESULTS

In all, 112 out of 127 (88%) patients successfully transferred to sulfonylureas from insulin with an improvement in HbA1c from 8.2% (66 mmol/mol) on insulin, to 5.9% (41 mmol/mol) on sulphonylureas (p = 0.001). The in vitro response of the mutation to tolbutamide determined the likelihood of transfer: the extent of tolbutamide block was <63% for the p.C166Y, p.I296L, p.L164P or p.T293N mutations, and no patients with these mutations successfully transferred. However, most individuals with mutations for which tolbutamide block was >73% did transfer successfully. The few patients with these mutations who could not transfer had a longer duration of diabetes than those who transferred successfully (18.2 vs 3.4 years, p = 0.032). There was no difference in pre-transfer HbA1c (p = 0.87), weight-for-age z scores (SD score; p = 0.12) or sex (p = 0.17).

CONCLUSIONS/INTERPRETATION

Transfer from insulin is successful for most KCNJ11 patients and is best predicted by the in vitro response of the specific mutation and the duration of diabetes. Knowledge of the specific mutation and of diabetes duration can help predict whether successful transfer to sulfonylureas is likely. This result supports the early genetic testing and early treatment of patients with neonatal diabetes aged under 6 months.

Neonatal diabetes and protein losing enteropathy: a case report

Background

Neonatal diabetes is a rare form of monogenic diabetes with onset in the first six months of life occurring in 1/100,000 to 1/400,000 births. Both permanent and transient forms have been described. Permanent neonatal diabetes results predominantly from mutations in the KCNJ11 and ABCC8 genes. Less frequently, mutations of the GATA6 gene, located on chromosome 18 cause a form of permanent neonatal diabetes resulting from pancreatic hypoplasia or agenesis. Other anomalies associated with mutations of this gene have also been reported, most commonly congenital heart disease.

Case presentation

We report the case of a Caucasian male infant diagnosed shortly after birth with neonatal diabetes, truncus arteriosus type III, ventricular septal defect, atrial septal defect, an absent gallbladder and a right inguinal hernia. His diabetes resulted from a de novo mutation of the GATA6 gene resulting in pancreatic hypoplasia. At 20 months of age he developed protein losing enteropathy. This has not previously been associated with GATA6 mutations and it is not known if this association is causal.

Conclusion

The combination of neonatal diabetes and pancreatic agenesis/hypoplasia should alert the clinician to the possibility of a GATA6 gene abnormality. The association of protein losing enteropathy is unique to the reported case.

Mitochondrial Complex III Deficiency with Ketoacidosis and Hyperglycemia Mimicking Neonatal Diabetes

Hyperglycemia is a rare presenting symptom of mitochondrial disorders. We report a case of a young girl who presented shortly after birth with ketoacidosis, hyperlactatemia, hyperammonemia, and insulin-responsive hyperglycemia. Initial metabolic work-up suggested mitochondrial dysfunction. Given our patient's unusual presentation, whole-exome sequencing (WES) was performed on the parent-offspring trio. The patient was homozygous for the c.643C>T (p.Leu215Phe) variant in CYC1, a nuclear gene which encodes cytochrome c ₁ , a subunit of respiratory chain complex III. Variants in this gene have only been previously reported in two patients with similar presentation, one of whom carries the same variant as our patient who is also of Sri Lankan origin.Primary complex III deficiencies are rare and its phenotypes can vary significantly, even among patients with the same genotype.

Genome, Exome, and Targeted Next-Generation Sequencing in Neonatal Diabetes

The use of targeted gene panels now allows the analysis of all the genes known to cause a disease in a single test. For neonatal diabetes, this has resulted in a paradigm shift with patients receiving a genetic diagnosis early and the genetic results guiding their clinical management. Exome and genome sequencing are powerful tools to identify novel genetic causes of known diseases. For neonatal diabetes, the use of these technologies has resulted in the identification of 2 novel disease genes (GATA6 and STAT3) and a novel regulatory element of PTF1A, in which mutations cause pancreatic agenesis.

Molecular genetic testing of patients with monogenic diabetes and hyperinsulinism

Genetic sequencing has become a critical part of the diagnosis of certain forms of pancreatic beta cell dysfunction. Despite great advances in the speed and cost of DNA sequencing, determining the pathogenicity of variants remains a challenge, and requires sharing of sequence and phenotypic data between laboratories. We reviewed all diabetes and hyperinsulinism-associated molecular testing done at the Seattle Children's Molecular Genetics Laboratory from 2009 to 2013. 331 probands were referred to us for molecular genetic sequencing for Neonatal Diabetes (NDM), Maturity-Onset Diabetes of the Young (MODY), or Congenital Hyperinsulinism (CHI) during this period. Reportable variants were identified in 115 (35%) patients with 91 variants in one of 6 genes: HNF1A, GCK, HNF4A, ABCC8, KCNJ11, or INS. In addition to identifying 23 novel variants, we identified unusual mechanisms of inheritance, including mosaic and digenic MODY presentations. Re-analysis of all reported variants using more recently available databases led to a change in variant interpretation from the original report in 30% of cases. These results represent a resource for molecular testing of monogenic forms of diabetes and hyperinsulinism, providing a mutation spectrum for these disorders in a large North American cohort. In addition, they highlight the importance of periodic review of molecular testing results.

Update on diabetes classification

This article highlights the difficulties in creating a definitive classification of diabetes mellitus in the absence of a complete understanding of the pathogenesis of the major forms. This brief review shows the evolving nature of the classification of diabetes mellitus. No classification scheme is ideal, and all have some overlap and inconsistencies. The only diabetes in which it is possible to accurately diagnose by DNA sequencing, monogenic diabetes, remains undiagnosed in more than 90% of the individuals who have diabetes caused by one of the known gene mutations. The point of classification, or taxonomy, of disease, should be to give insight into both pathogenesis and treatment. It remains a source of frustration that all schemes of diabetes mellitus continue to fall short of this goal.