Six cases with severe insulin resistance (SIR) associated with mutations of insulin receptor: Is a Bartter-like syndrome a feature of congenital SIR?

Case report: A case of Rabson-Mendenhall syndrome: long-term follow-up and therapeutic management with empagliflozin

Background: Rabson-Mendenhall syndrome (RMS), a rare disorder characterized by severe insulin resistance due to biallelic loss-of-function variants of the insulin receptor gene (INSR), presents therapeutic challenges (OMIM: 262190). This case study explores the efficacy of adjunctive therapy with sodium-glucose cotransporter 2 inhibitors (SGLT2is) in the management of RMS in an 11-year-old male patient with compound heterozygous pathogenic variants of INSR. Methods: Despite initial efforts to regulate glycemia with insulin therapy followed by metformin treatment, achieving stable glycemic control presented a critical challenge, characterized by persistent hyperinsulinism and variable fluctuations in glucose levels. Upon the addition of empagliflozin to metformin, notable improvements in glycated hemoglobin (HbA1c) and time in range (TIR) were observed over a 10-month period. Results: After 10 months of treatment, empagliflozin therapy led to a clinically meaningful reduction in HbA1c levels, decreasing from 8.5% to 7.1%, along with an improvement in TIR from 47% to 74%. Furthermore, regular monitoring effectively averted normoglycemic ketoacidosis, a rare complication associated with SGLT2 inhibitor therapy. Conclusion: This case highlights the potential of SGLT2i as adjunctive therapy in RMS management, particularly in stabilizing glycemic variability. However, further research is warranted to elucidate the long-term efficacy and safety of this therapeutic approach in RMS and similar insulin resistance syndromes.

Monogenic diabetes clinic (MDC): 3-year experience

AIM

In the pediatric diabetes clinic, patients with type 1 diabetes mellitus (T1D) account for more than 90% of cases, while monogenic forms represent about 6%. Many monogenic diabetes subtypes may respond to therapies other than insulin and have chronic diabetes complication prognosis that is different from T1D. With the aim of providing a better diagnostic pipeline and a tailored care for patients with monogenic diabetes, we set up a monogenic diabetes clinic (MDC).

METHODS

In the first 3 years of activity 97 patients with non-autoimmune forms of hyperglycemia were referred to MDC. Genetic testing was requested for 80 patients and 68 genetic reports were available for review.

RESULTS

In 58 subjects hyperglycemia was discovered beyond 1 year of age (Group 1) and in 10 before 1 year of age (Group 2). Genetic variants considered causative of hyperglycemia were identified in 25 and 6 patients of Group 1 and 2, respectively, with a pick up rate of 43.1% (25/58) for Group 1 and 60% (6/10) for Group 2 (global pick-up rate: 45.5%; 31/68). When we considered probands of Group 1 with a parental history of hyperglycemia, 58.3% (21/36) had a positive genetic test for GCK or HNF1A genes, while pick-up rate was 18.1% (4/22) in patients with mute family history for diabetes. Specific treatments for each condition were administered in most cases.

CONCLUSION

We conclude that MDC may contribute to provide a better diabetes care in the pediatric setting.

INSR novel mutations identified in a Chinese family with severe INSR-related insulin resistance syndromes: A case report

RATIONALE

Severe insulin receptor gene (INSR)-related insulin resistance syndromes (SIR) include Donohue syndrome (DS), Rabson-Mendenhall syndrome (RMS), and type A insulin resistance. The incidence of DS is about 1 in 4 million births. We identified novel INSR mutations (c.2246delG and c.2646 + 5G > A) in a patient with SIR, which expanded the variant spectrum and helped to improve the understanding of the diagnosis and treatment of this condition.

PATIENT CONCERNS

A 10-year-old Chinese boy was admitted to the hospital for deepening skin color. He presented with growth retardation, peculiar facial features, acanthosis nigricans, hypertrichosis, extremely high insulin levels, fasting hypoglycemia, and postprandial hyperglycemia, Whole-exome gene testing suggested compound heterozygous mutations in INSR (c.2246delG and c.2646 + 5G > A).

DIAGNOSIS

The diagnosis was SIR. What's more, based on the phenotypic and biographical results, this child did not present typical RMS and DS but rather an intermediate phenotype between the 2 conditions.

INTERVENTIONS

On the basis of a sensible diet and exercise, the patient was prescribed metformin (250 mg) at breakfast and lunch, which was increased to 500 mg after 1 month.

OUTCOMES

After 2 months of treatment, the patient's glycated hemoglobin (HbA1c) levels decreased to 6% but his insulin resistance did not improve significantly.

LESSONS

In children who are not obese but with severe insulin resistance, growth retardation, hirsutism, and hyperglycemia, genetic testing should be performed for early diagnosis, active treatment, and follow-up.

Activation of the insulin receptor by an insulin mimetic peptide

Insulin receptor (IR) signaling defects cause a variety of metabolic diseases including diabetes. Moreover, inherited mutations of the IR cause severe insulin resistance, leading to early morbidity and mortality with limited therapeutic options. A previously reported selective IR agonist without sequence homology to insulin, S597, activates IR and mimics insulin's action on glycemic control. To elucidate the mechanism of IR activation by S597, we determine cryo-EM structures of the mouse IR/S597 complex. Unlike the compact T-shaped active IR resulting from the binding of four insulins to two distinct sites, two S597 molecules induce and stabilize an extended T-shaped IR through the simultaneous binding to both the L1 domain of one protomer and the FnIII-1 domain of another. Importantly, S597 fully activates IR mutants that disrupt insulin binding or destabilize the insulin-induced compact T-shape, thus eliciting insulin-like signaling. S597 also selectively activates IR signaling among different tissues and triggers IR endocytosis in the liver. Overall, our structural and functional studies guide future efforts to develop insulin mimetics targeting insulin resistance caused by defects in insulin binding and stabilization of insulin-activated state of IR, demonstrating the potential of structure-based drug design for insulin-resistant diseases.

SGLT2i Improves Glycemic Control in Patients With Congenital Severe Insulin Resistance

Insulin-resistant diabetes in Rabson-Mendenhall syndrome (RMS) is relatively unresponsive to first-line antidiabetic treatments, including metformin and insulin. We report 2 patients with RMS treated with 2 different sodium-glucose cotransporter inhibitors 2: empagliflozin in an 11-year-old boy and dapagliflozin in a 12-year-old girl. In the first patient, we began empagliflozin at 2.5 mg/day and increased the dose to 10 mg/day over 3 months. During treatment with empagliflozin, the amount of time during which the patient maintained serum glucose in the 70 to 180 mg/dL target range increased by 2 hours per day. Hemoglobin A1C dropped from >14% to 11.9%, urinary calcium increased almost twofold, and β-hydroxybutyrate remained <2.5 mmol/L. Because glycemic control did not further improve with dose escalation, we reverted to the 2.5 mg/day dose. We initiated dapagliflozin in a second patient at 5 mg/day and witnessed a reduction of hemoglobin A1C from 8.5% to 6.2% after 6 months and a mild increase in urinary excretion of phosphorus but not calcium. Insulin levels fell by >50%. In 2 patients with RMS, empagliflozin and dapagliflozin were well tolerated and improved glycemic control without significantly increasing ketonemia. Renal calcium excretion should be carefully monitored.

Severe insulin resistance syndromes

Severe insulin resistance syndromes are a heterogeneous group of rare disorders characterized by profound insulin resistance, substantial metabolic abnormalities, and a variety of clinical manifestations and complications. The etiology of these syndromes may be hereditary or acquired, due to defects in insulin potency and action, cellular responsiveness to insulin, and/or aberrations in adipose tissue function or development. Over the past decades, advances in medical technology, particularly in genomic technologies and genetic analyses, have provided insights into the underlying pathophysiological pathways and facilitated the more precise identification of several of these conditions. However, the exact cellular and molecular mechanisms of insulin resistance have not yet been fully elucidated for all syndromes. Moreover, in clinical practice, many of the syndromes are often misdiagnosed or underdiagnosed. The majority of these disorders associate with an increased risk of severe complications and mortality; thus, early identification and personalized clinical management are of the essence. This Review aims to categorize severe insulin resistance syndromes by disease process, including insulin receptor defects, signaling defects, and lipodystrophies. We also highlight several complex syndromes and emphasize the need to identify patients, investigate underlying disease mechanisms, and develop specific treatment regimens.

A New Mutation of the INSR Gene in a 13-Year-Old Girl with Severe Insulin Resistance Syndrome in China

Background

Mutations in insulin receptor genes can cause severe insulin resistance syndrome. Compared with Rabson-Mendenhall Syndrome and Donohue's Syndrome, type A insulin resistance syndrome is generally not serious. The main manifestations in woman with type A insulin resistance syndrome are hyperinsulinemia, insulin resistance, acanthosis nigricans, hyperandrogenism, and polycystic ovary. Case Presentation. A 13-year-old girl (Han nationality) visited the hospital due to hairiness and acanthosis nigricans. Further examination revealed severe hyperinsulinemia, insulin resistance, elevated blood glucose, hyperandrogenism, and polycystic ovary. Analysis of the insulin receptor gene by sequencing showed the presence of a nucleotide change in intron 7 (c. 1610+1G > A). The mutation was a splicing mutation, which can obviously affect the mRNA splicing of the insulin receptor and cause its function loss. The patient was finally diagnosed with type A insulin resistance syndrome. After 2 months of metformin treatment, the patient had spontaneous menstrual cramps and significantly improved acanthosis nigricans and sex hormones.

Conclusion

We report for the first time a new splicing mutation on the insulin receptor gene at the 7th intron (c.1610+1G > A), which leads to type A insulin resistance syndrome. In clinically suspected patients with polycystic ovary syndrome, if there are extremely high blood levels of insulin in the blood, genetic testing should be performed to detect insulin receptor gene mutation of type A insulin resistance syndrome.

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.

Clinical and Functional Characterization of Novel INSR Variants in Two Families With Severe Insulin Resistance Syndrome

OBJECTIVE

Defects in the insulin receptor (INSR) gene cause various severe insulin resistance conditions, including Donohue syndrome (DS), Rabson-Mendenhall syndrome (RMS) and type A insulin resistance (type A-IR). This study aimed to investigate the clinical characterization and molecular defects in three Chinese children with INSR-related insulin resistance syndrome.

METHODS

We reviewed the clinical data of three Chinese children with INSR-related insulin resistance syndrome from two unrelated kindreds. Genetic analysis was performed using whole-exome sequencing and the effects of the novel variants were further assessed by in vitro functional assays.

RESULTS

The proband with type A-IR presented with acanthosis nigricans, hypertrichosis, and euglycemia with mild insulin resistance in early childhood. His sister presented with features typical of type A-IR and was diagnosed with diabetes mellitus with severe insulin resistance at the age of 9.8 years. The proband with DS showed typical dysmorphic characteristics, severe intrauterine growth retardation, extreme insulin resistance, fasting hypoglycemia and postprandial hyperglycemia from birth. The heterozygote variants c.[3670G>A]; c.[3614C>T] were identified in both siblings with type A-IR; and c.[749_751del]; c.[3355C>T] in the patient with DS. In vitro studies showed that the novel variant c.749_751del [p.(Thr250del)] in the α-subunit, reduced expression of the mature INSR protein and severely impaired INSR function. In contrast, the novel variant c.3670G>A [p.(Val1224Met)] in the β-subunit had no effect on total protein expression and phosphorylation of INSR and Akt, suggesting that the variant p.Val1224Met appeared to be tolerated and was not responsible for the severe insulin resistance.

CONCLUSION

Our study detailed the clinical features of three patients with type A-IR and DS, and identified two novel variants in the INSR gene. Functional assays indicated the novel variant p.Thr250del was pathogenic. In contrast, the novel variant p.Val1224Met was suggested to be tolerated by our experimental data, even though bioinformatics analyses predicted the variant as deleterious.

Two Novel Variants and One Previously Reported Variant in the Insulin Receptor Gene in Two Cases with Severe Insulin Resistance Syndrome

Donohue syndrome (DS) and Rabson-Mendenhall syndrome (RMS) are rare diseases caused by biallelic variants within the insulin receptor gene (INSR). Here, we report 2 cases: one with DS and the other with RMS. The case with DS presented with intrauterine growth retardation, nipple hypertrophy, clitoromegaly, distended abdomen, hypertrichosis, and dysmorphic features. The second case showed severe acanthosis nigricans, hyperkeratosis, and hypertrichosis. In both cases, abnormal glucose homeostasis due to severe insulin resistance was observed. The diagnosis of DS and RMS was established based on clinical characteristics, abnormal glucose homeostasis, high serum insulin levels, and determination of pathogenic variants in the INSR gene. The first case with DS has 2 novel homozygous variants, NM_000208.3, c.3122delA (p.N1041Mfs*16) and c.3419C>G (p.A1140G), and the second case with RMS has a previously reported homozygous variant NM_000208.3, c.3529+5G>A (IVS19+5G>A) in the INSR gene.

Congenital diabetes mellitus

Congenital diabetes mellitus is a rare disorder characterized by hyperglycemia that occurs shortly after birth. We define "Diabetes of Infancy" if hyperglycemia onset before 6 months of life. From the clinical point of view, we distinguish two main types of diabetes of infancy: transient (TNDM), which remits spontaneously, and permanent (PNDM), which requires lifelong treatment. TNDM may relapse later in life. About 50% of cases are transient (TNDM) and 50% permanent. Clinical manifestations include severe intrauterine growth retardation, hyperglycemia and dehydration. A wide range of different associated clinical signs including facial dysmorphism, deafness and neurological, cardiac, kidney or urinary tract anomalies are reported. Developmental delay and learning difficulties may also be observed. In this paper we review all the causes of congenital diabetes and all genes and syndromes involved in this pathology. The discovery of the pathogenesis of most forms of congenital diabetes has made it possible to adapt the therapy to the diagnosis and in the forms of alteration of the potassium channels of the pancreatic Beta cells the switch from insulin to glibenclamide per os has greatly improved the quality of life. Congenital diabetes, although it is a very rare form, has been at the must of research in recent years especially for pathogenesis and pharmacogenetics. The most striking difference compared to the more frequent autoimmune diabetes in children (type 1 diabetes) is the possibility of treatment with hypoglycemic agents and the apparent lower frequency of chronic complications.

Clinical characteristics of adolescent cases with Type A insulin resistance syndrome caused by heterozygous mutations in the β-subunit of the insulin receptor (INSR) gene

BACKGROUND

Type A insulin resistance (IR) is a rare form of severe congenital IR that is frequently caused by heterozygous mutations in the insulin receptor (INSR) gene. Although Type A IR requires appropriate intervention from the early stages of diabetes, proper diagnosis of this disease is challenging, and accumulation of cases with detailed clinical profiles and genotypes is required.

METHODS

Herein we report on six peripubertal patients with clinically diagnosed Type A IR, including four patients with an identified INSR mutation. To clarify the clinical features of Type A IR due to INSR mutation, we validated the clinical characteristics of Type A IR patients with identified INSR mutations by comparing them with mutation-negative patients.

RESULTS

Four heterozygous missense mutations within the β-subunit of INSR were detected: Gly1146Arg, Arg1158Trp, Arg1201Trp, and one novel Arg1201Pro mutation. There were no obvious differences in clinical phenotypes, except for normal lipid metabolism and autosomal dominant inheritance, between Type A IR due to INSR mutations and Type A IR due to other factors. However, our analysis revealed that the extent of growth retardation during the fetal period is correlated with the severity of insulin signaling impairment.

CONCLUSIONS

The present study details the clinical features of four patients with genetically proven Type A IR. Further accumulation of genetically proven cases and long-term treatment prognoses following early diagnosis are required to further elucidate the dynamics of this disease.

Genetic causes and treatment of neonatal diabetes and early childhood diabetes

Diabetes mellitus and impaired fasting glucose associated with single gene mutations are less rare than previously thought and may account for more than 6% of patients attending a pediatric diabetes clinic. The number of loci involved in monogenic diabetes exceed 25, and appropriate genetic diagnosis is crucial to direct therapy, for genetic counseling and for prognosis of short- and long-term complications. Among patients with neonatal diabetes (i.e. with onset within first 6 months of life) and patients with Maturity Onset Diabetes of the Young (MODY; an autosomal dominant form of diabetes), those carrying mutations in KCNJ11, ABCC8, HNF1A and HNF4A genes usually respond to oral therapy with sulphonylurea, while those bearing GCK mutations do not necessitate any treatment. Sensor-augmented continuous subcutaneous insulin infusion has been successfully employed in neonatal diabetes, and long-lasting effectiveness of sulfonylurea in KCNJ11 mutation carriers with neonatal diabetes well documented.

One Novel 2.43Kb Deletion and One Single Nucleotide Mutation of the INSR Gene in a Chinese Neonate with Rabson-Mendenhall Syndrome

Mutations in the insulin receptor (INSR) gene are responsible for Donohue syndrome (DS) and Rabson-Mendenhall syndrome (RMS). Insulin resistance is a feature of both diseases. Our patient was a Chinese neonate suffering from abnormal glucose homeostasis, hyperinsulinemia, dry skin, heavy hair, growth retardation and an elevated testosterone level. To search for candidate point mutations, small insertions or deletions and copy number variants, 2742 inherited disease-gene panel sequencing was performed. One pathogenic mutation (c.3355C>T, p.Arg1119Trp) and a novel 2.43Kb deletion (chr19:7150507-7152938) in INSR were found. The patient was diagnosed as RMS. Sanger sequencing and real-time quantitative polymerase chain reaction (PCR) confirmed the missense variant and microdeletion, respectively. We therefore supposed that these variants were candidate mutations in this case. We report a novel 2.43Kb deletion in INSR gene and provide further proof of the power of next generation sequencing in rare disease diagnosis.

Severe insulin resistance in disguise: A familial case of reactive hypoglycemia associated with a novel heterozygous INSR mutation

AIM

Hypoglycemia in childhood is very rare and can be caused by genetic mutations or insulin-secreting neoplasms. Postprandial hypoglycemia has previously been associated with insulin receptor (INSR) gene mutations. We aimed to identify the cause of postprandial hypoglycemia in a 10-year-old boy.

SUBJECTS

We studied the symptomatic proband and his apparently asymptomatic mother and elder brother. All of them were lean.

METHODS

Metabolic screening of the proband included a 5-hour oral glucose tolerance test (OGTT), angio-magnetic resonance imaging, and ¹⁸ F-dihydroxyphenylalanine positron emission tomography/computed tomography imaging of the pancreas. INSR gene sequencing and in vitro functional studies of a novel INSR mutation were also undertaken.

RESULTS

Fasting hyperinsulinemia was detected during metabolic screening, and 5-hour OGTT showed hypoglycemia at 240' in the proband, his mother, and brother. Pancreatic imaging showed no evidence of neoplasia. Acanthosis nigricans with high fasting insulin levels in the proband suggested severe insulin resistance and prompted INSR gene sequencing, which revealed the novel, heterozygous p.Phe1213Leu mutation in the patient and his family members. In vitro studies showed that this mutation severely impairs insulin receptor function by abolishing tyrosine kinase activity and downstream insulin signaling.

CONCLUSIONS

The identification of etiological cause of hypoglycemia in childhood may be challenging. The combination of fasting hyperinsulinemia with acanthosis nigricans in a lean subject with hypoglycemia suggests severe insulin resistance and warrants INSR gene screening.

Mecasermin in Insulin Receptor-Related Severe Insulin Resistance Syndromes: Case Report and Review of the Literature

Mutations in the insulin receptor (INSR) gene underlie rare severe INSR-related insulin resistance syndromes (SIR), including insulin resistance type A, Rabson–Mendenhall syndrome and Donohue syndrome (DS), with DS representing the most severe form of insulin resistance. Treatment of these cases is challenging, with the majority of DS patients dying within the first two years of life. rhIGF-I (mecasermin) has been reported to improve metabolic control and increase lifespan in DS patients. A case report and literature review were completed. We present a case involving a male patient with DS, harbouring a homozygous mutation in the INSR gene (c.591delC). Initial rhIGF-I application via BID (twice daily) injection was unsatisfactory, but continuous subcutaneous rhIGF-I infusion via an insulin pump improved weight development and diabetes control (HbA1c decreased from 10 to 7.6%). However, our patient died at 22 months of age during the course of a respiratory infection in in Libya. Currently available data in the literature comprising more than 30 treated patients worldwide seem to support a trial of rhIGF-I in SIR. rhIGF-I represents a treatment option for challenging SIR cases, but careful consideration of the therapeutic benefits and the burden of the disease is warranted. Continuous application via pump might be advantageous compared to single injections.

Structural Basis and Genotype-Phenotype Correlations of INSR Mutations Causing Severe Insulin Resistance

The insulin receptor (INSR) gene was analyzed in four patients with severe insulin resistance, revealing five novel mutations and a deletion that removed exon 2. A patient with Donohue syndrome (DS) had a novel p.V657F mutation in the second fibronectin type III domain (FnIII-2), which contains the α-β cleavage site and part of the insulin-binding site. The mutant INSR was expressed in Chinese hamster ovary cells, revealing that it reduced insulin proreceptor processing and impaired activation of downstream signaling cascades. Using online databases, we analyzed 82 INSR missense mutations and demonstrated that mutations causing DS were more frequently located in the FnIII domains than those causing the milder type A insulin resistance (P = 0.016). In silico structural analysis revealed that missense mutations predicted to severely impair hydrophobic core formation and stability of the FnIII domains all caused DS, whereas those predicted to produce localized destabilization and to not affect folding of the FnIII domains all caused the less severe Rabson-Mendenhall syndrome. These results suggest the importance of the FnIII domains, provide insight into the molecular mechanism of severe insulin resistance, will aid early diagnosis, and will provide potential novel targets for treating extreme insulin resistance.

Monogenic Diabetes Accounts for 6.3% of Cases Referred to 15 Italian Pediatric Diabetes Centers During 2007 to 2012

CONTEXT

An etiologic diagnosis of diabetes can affect the therapeutic strategy and prognosis of chronic complications.

OBJECTIVE

The aim of the present study was to establish the relative percentage of different diabetes subtypes in patients attending Italian pediatric diabetes centers and the influence of an etiologic diagnosis on therapy.

DESIGN, SETTING, AND PATIENTS

This was a retrospective study. The clinical records of 3781 consecutive patients (age, 0 to 18 years) referred to 15 pediatric diabetes clinics with a diagnosis of diabetes or impaired fasting glucose from January 1, 2007 to December 31, 2012 were examined. The clinical characteristics of the patients at their first referral to the centers, type 1 diabetes-related autoantibodies, molecular genetics records, and C-peptide measurements, if requested for the etiologic diagnosis, were acquired.

MAIN OUTCOME MEASURES

The primary outcome was to assess the percentage of each diabetes subtype in our sample.

RESULTS

Type 1 diabetes represented the main cause (92.4%) of diabetes in this group of patients, followed by monogenic diabetes, which accounted for 6.3% of cases [maturity onset diabetes of the young (MODY), 5.5%; neonatal diabetes mellitus, 0.6%, genetic syndromes, 0.2%]. A genetic diagnosis prompted the transfer from insulin to sulphonylureas in 12 patients bearing mutations in the HNF1A or KCNJ11 genes. Type 2 diabetes was diagnosed in 1% of the patients.

CONCLUSIONS

Monogenic diabetes is highly prevalent in patients referred to Italian pediatric diabetes centers. A genetic diagnosis guided the therapeutic decisions, allowed the formulation of a prognosis regarding chronic diabetic complications for a relevant number of patients (i.e.,GCK/MODY), and helped to provide genetic counseling.

Treatment of Diabetic Ketoacidosis With Intravenous U-500 Insulin in a Patient With Rabson-Mendenhall Syndrome: A Case Report

Rabson-Mendenhall syndrome is a rare genetic disorder resulting from mutations in the insulin receptor and is associated with high degrees of insulin resistance. These patients are prone to complications secondary to their hyperglycemia including diabetic ketoacidosis (DKA). We report the case of a 19-year-old male with Rabson-Mendenhall syndrome presenting with DKA who required doses of up to 500 U/h (10.6 U/kg/h) of insulin. The patient's insulin infusion was originally compounded with U-100 regular insulin, although to minimize volume, the product was compounded with U-500 insulin. The DKA eventually resolved requiring infusion rates ranging from 400 to 500 U/h. Although numerous opportunities for medication errors exist with the use of U-500 insulin, this case outlines the safe use of concentrated intravenous insulin when clinically indicated for patients requiring extremely high doses of insulin to control blood glucose.

First molecular diagnosis of Donohue syndrome in Africa: novel unusual insertion/deletion mutation in the INSR gene

Donohue syndrome (DS) is a very rare autosomal recessive disease affecting less than one in a million life births. It represents the most severe form of insulin resistance due to mutations involving the insulin receptor (IR) gene "INSR". DS is characterized by pre- and postnatal growth retardation with failure-to-thrive, lipoatrophy, acanthosis nigricans, hypertrichosis, and dysmorphic features. An exhaustive INSR gene sequencing was performed after PCR amplification of coding exons and introns boundaries. Bioinformatic tools, including ESEfinder, MFOLD and Proter software were also used to predict the impact of INSR mutation on INSR on gene expression as well as on the protein structure and function. The results have shown a novel unusual c.3003_3012delinsGGAAG (p.S1001_D1004delinsRE) insertion/deletion (indel) mutation within the exon 16 in the three patients, which represent the fourth indel mutation within the INSR gene. The mutation modifies the secondary structure of DNA and RNA, as well as the composition of exonic splicing enhancers of exon 16. Moreover, despite the conservation of the secondary structure of the IR, the p.S1001_D1004delinsRE in-frame mutation is accompanied by the loss of four amino acids replaced by two residues of different nature and hydrophobicity level in the juxtamembrane domain of the receptor. The results have confirmed the role of the juxtamembrane domain of IR involved in a crucial interaction of the IR with cellular effectors essentially the IR substrate 1 (IRS-1), the SHC and the Nck proteins that ensure the signal mediated by the insulin transduction pathway in target cells. Our findings have also proven the genotype/phenotype correlation between INSR mutation and DS phenotype severity.

Classic Case Report of Donohue Syndrome (Leprechaunism; OMIM *246200): The Impact of Consanguineous Mating

Donohue syndrome ([DS]; leprechaunism) describes a genetic autosomal recessive disorder that results from the presence of homozygous or compound heterozygous mutations in the insulin receptor gene (INSR; 19p13.3-p13.2).Donohue syndrome is associated with a fatal congenital form of dwarfism with features of intrauterine and postnatal growth retardation, exaggerated hyperglycemia with hyperinsulinism and dysmorphic abnormalities.We present a case of DS owing to the rarity of this syndrome (1 case in every million births). We discuss how the disease presents, its genetic underpinning, and its prevention.The case was encountered in an Arab male born on 1 September, 2014, for consanguineous parents. The delivery was via cesarean section at 37 weeks gestation due to severe intrauterine growth restriction and nonprogress labor term. The patient was admitted to the Neonatal Intensive Care Unit due to infection, and jaundice. Dysmorphic features, abnormalities of the craniofacial region, low birth weight, skin abnormalities, abdominal distension and hypertrichosis were observed. Laboratory examinations showed, hyperinsulinism, increased C-peptide, thrombocytopenia, leucopenia, and anemia.The diagnosis of DS was done based on the combinations of typical dysmorphic characteristics, clinical evaluation, supported by genetic analysis and exaggerated biochemical results. Genetic diagnosis of DS was performed through analysis of DNA via polymerase chain reaction (PCR). A qualitative real-time PCR was used, to monitor the amplification of a targeted DNA molecule during the PCR. Other technique using sequencing of the INSR gene, which permits genetic diagnosis, counseling, and antenatal diagnoses in subsequent pregnancies, were also performed.Treatment of DS is supportive and requires the combined efforts of a multidisciplinary team, which include pediatricians, endocrinologists, dermatologists, and other health care professionals. Currently, treatment with recombinant insulin-like growth factor 1 demonstrates effectiveness, and a combination treatment with insulin-like growth factor binding protein 3 resulted in an increased lifespan.There is a scarcity of genetic information on DS among the Arab population. Consanguinity is one of underlying reasons for the appearance of rare genetic disorders. Inbreeding has long been considered a controversial phenomenon. Genetic counseling and overwhelming the alertness of the negative consequences of consanguinity on public health are warranted.

Case Report: When an Induced Illness Looks Like a Rare Disease

The recognition of fabricated illness (FI) in a child represents a diagnostic challenge. The suspicion of FI often arises from the discrepancy between laboratory tests and clinical history. For instance, (unnecessary) insulin injections by caregivers has been widely described as a common cause of factitious hypoglycemia that may be inferred from discrepancies between plasma insulin and c-peptide. However, contemporary administration of insulin with an insulin secretagogue (glyburide), and of additional drugs, can make the diagnostic pathway problematic. We report the case of a child 4 years and 11 months old, admitted for alternance of hypo- and hyperglycemia associated with hirsutism, hypokalemia, nephrocalcinosis, and neurodevelopmental delay. All these features were compatible with Rabson-Mendenhall syndrome, a rare disorder of severe insulin resistance linked to mutations of insulin receptor. At admission, plasma insulin levels were high during hypoglycemic episodes, but c-peptide was repeatedly in the normal range. The genetic analysis of insulin receptor was negative. The story of previous hospital admissions, inconsistency between insulin and c-peptide values, and association between hypoglycemic episodes in the child with the presence of the mother, raised the suspicion of FI. This hypothesis was confirmed by a video recording that revealed the administration by the mother of multiple drugs (insulin, glyburide, progesterone, and furosemide) that mimicked most of the features of Rabson-Mendenhall syndrome, including hirsutism and hypoglycemia with coincident, inappropriately normal c-peptide values due to the administration of the insulin secretagogue. Our case indicates that inconsistency among consecutive diagnostic tests should be regarded as a clue of FI.

Paediatrics, insulin resistance and the kidney

Systemic insulin resistance is becoming more prevalent in the young due to modern lifestyles predisposing to the metabolic syndrome and obesity. There is also evidence that there are critical insulin-resistant phases for the developing child, including puberty, and that renal disease per se causes systemic insulin resistance. This review considers the factors that render children insulin resistant, as well as the accumulating evidence that the kidney is an insulin-responsive organ and could be affected by insulin resistance.

Donohue syndrome: a new case with a new complication

Donohue syndrome (DS) is a very rare autosomal recessive disease affecting less than one in a million live births. It represents the most severe form of insulin resistance due to mutations involving the insulin receptor gene. DS is characterized by pre- and postnatal growth retardation with failure to thrive, lipoatrophy, muscle wasting, acanthosis nigricans, hypertrichosis, and dysmorphic features. Glucose homeostasis is affected with hyperinsulinemia, fasting hypoglycemia, and postprandial hyperglycemia. We report a Jordanian patient with genetically proven DS who had the classical physical features, progressive hypertrophic cardiomyopathy, cholestasis, and hyperglycemia, followed by hypoglycemia. In addition, the patient developed polyuria and uremia despite normal creatinine levels, hypernatremia, and hypertension. To our knowledge, these metabolic derangements were not previously reported in patients with DS.

Insulin Receptor and the Kidney: Nephrocalcinosis in Patients with Recessive INSR Mutations

BACKGROUND/AIMS

Donohue and Rabson-Mendenhall syndrome are rare autosomal recessive disorders caused by mutations in the insulin receptor gene, INSR. Phenotypic features include extreme insulin resistance, linear growth retardation, paucity of fat and muscle, and soft tissue overgrowth. The insulin receptor is also expressed in the kidney, where animal data suggest it plays a role in glomerular function and blood pressure (BP) regulation, yet such a role in the human kidney is untested. Patients with biallelic INSR mutations provide a rare opportunity to ascertain its role in man.

METHODS

Retrospective review of patients with INSR mutations. Data for BP, renal imaging, plasma creatinine and electrolyte levels, as well as urine protein, albumin and calcium excretion were sought from the treating clinicians.

RESULTS

From 33 patients with INSR mutations, data were available for 17 patients. Plasma creatinine was low (mean ± SD: 25 ± 9 μmol/l) and mean plasma electrolyte concentrations were within the normal range (n = 13). Systolic BP ranged between the 18th and 91st percentile for age, sex, height and weight (n = 9; mean ± SD: 49 ± 24). Twenty-four-hour urinary calcium data were available from 10 patients and revealed hypercalciuria in all (mean ± SD: 0.32 ± 0.17 mmol/kg/day; normal <0.1). Nephrocalcinosis was present in all patients (n = 17). Urinary albumin excretion (n = 7) ranged from 4.3-122.5 μg/min (mean ± SD: 32.4 ± 41.0 μg/min; normal <20).

CONCLUSIONS

INSR dysfunction is associated with hypercalciuria and nephrocalcinosis. No other consistent abnormality of renal function was noted. Normotension and stable glomerular function with only moderate proteinuria is in contrast to genetically modified mice who have elevated BP and progressive diabetic nephropathy.

Sequencing analysis of insulin receptor defects and detection of two novel mutations in INSR gene

Mutations in the insulin receptor gene cause the inherited insulin resistant syndromes Leprechaunism and Rabson–Mendenhall syndrome. These recessive conditions are characterized by intrauterine and post-natal growth restrictions, dysmorphic features, altered glucose homeostasis, and early demise. The insulin receptor gene (INSR) maps to the short arm of chromosome 19 and is composed of 22 exons. Here we optimize the conditions for sequencing this gene and report novel mutations in patients with severe insulin resistance.

Methods

PCR amplification of the 22 coding exons of the INSR gene was performed using M13-tailed primers. Bidirectional DNA sequencing was performed with BigDye Terminator chemistry and M13 primers and the product was analyzed on the ABI 3100 genetic analyzer. Data analysis was performed using Mutation Surveyor software comparing the sequence to a reference INSR sequence (Genbank NC_000019).

Results

We sequenced four patients with Leprechaunism or Rabson–Mendenhall syndromes as well as seven samples from normal individuals and confirmed previously identified mutations in the affected patients. Three of the four mutations identified in this group caused premature insertion of a stop codon. In addition, the INSR gene was sequenced in 14 clinical samples from patients with suspected insulin resistance and one novel mutation was found in an infant with a suspected diagnosis of Leprechaunism.

Discussion

Leprechaunism and Rabson–Mendenhall syndrome are very rare and difficult to diagnose. Diagnosis is currently based mostly on clinical criteria. Clinical availability of DNA sequencing can provide an objective way of confirming or excluding the diagnosis.

Two novel mutations identified in familial cases with Donohue syndrome

Donohue syndrome (DS) is a rare and lethal autosomal recessive disease caused by mutations in the insulin receptor (INSR) gene, manifesting marked insulin resistance, severe growth retardation, hypertrichosis, and characteristic dysmorphic features. We report the clinical, molecular, and biochemical characterization of three new patients with DS, and address genotype–phenotype issues playing a role in the pathophysiology of DS. A female infant born to first-degree cousins Muslim Arab parents and two brothers born to first-degree cousins Druze parents presented classical features of DS with hypertrophic cardiomyopathy and died in infancy. Each patient was found homozygous for one missense mutation within the extracellular domain of the INSR gene. Western blot analysis identified the proreceptor of INSR, but not its mature subunits alpha and beta. Of 95 healthy Muslims, no heterozygous was found and of 52 healthy Druze from the same village, one was heterozygous. This study presents two novel familial mutations in the alpha subunit of the INSR which appear to impair post-translational processing of the INSR, resulting loss of its function. Both mutations cause DS with hypertrophic cardiomyopathy and early death. Identification of the causative mutation enables prevention of this devastating disease.