Fanconi-Bickel Syndrome Research Articles

Genetic, Clinical, and Biochemical Characterization ofa Large Cohort of Palestinian Patients With Fanconi-Bickel Syndrome.

This study aims to investigate the clinical, biochemical, and genetic characteristics of Fanconi-Bickel syndrome (FBS) in a cohort of 20 individuals from Palestine and to identify novel pathogenic variants. A retrospective analysis was conducted on medical records from Al-Makassed Hospital's pediatric department spanning 2015 to 2023. Individuals diagnosed with FBS via molecular genetic testing were included in the study. Among the 20 genetically confirmed FBS patients, hepatomegaly was prevalent in 95%, whereas 70% exhibited both developmental delay and hypophosphatemic rickets, and 68.4% experienced growth retardation. Hypertriglyceridemia (HTG) was universal. Elevated liver enzymes and alkaline phosphatase were common, along with hypophosphatemia (95%) and urinary abnormalities. Genetic analysis revealed five distinct SLC2A2 pathogenic variants, including three previously unreported variants: p.Gln23Arg (c.68A > G), p.Thr353Arg (c.1058_1059delinsGG), and an exon 7 deletion. This study presents the largest single-center cohort of FBS patients, expanding our understanding of the disorder's phenotypic and genotypic spectrum. Despite FBS generally carrying a favorable prognosis, timely diagnosis remains crucial to prevent severe complications.

Continuous glucose monitoring metrics in people with liver glycogen storage disease and idiopathic ketotic hypoglycemia: A single-center, retrospective, observational study

BackgroundCohort data on continuous glucose monitoring (CGM) metrics are scarce for liver glycogen storage diseases (GSDs) and idiopathic ketotic hypoglycemia (IKH). The aim of this study was to retrospectively describe CGM metrics for people with liver GSDs and IKH. Patients and methodsCGM metrics (descriptive, glycemic variation and glycemic control parameters) were calculated for 47 liver GSD and 14 IKH patients, categorized in cohorts by disease subtype, age and treatment status, and compared to published age-matched CGM metrics from healthy individuals. Glycemic control was assessed as time-in-range (TIR; ≥3.9 - ≤7.8 and ≥3.9 - ≤10.0 mmol/L), time-below-range (TBR; <3.0 mmol/L and ≥3.0 - ≤3.9 mmol/L), and time-above-range (TAR; >7.8 and >10.0 mmol/L). ResultsDespite all patients receiving dietary treatment, GSD cohorts displayed significantly different CGM metrics compared to healthy individuals. Decreased TIR together with increased TAR were noted in GSD I, GSD III, and GSD XI (Fanconi-Bickel syndrome) cohorts (all p < 0.05). In addition, all GSD I cohorts showed increased TBR (all p < 0.05). In GSD IV an increased TBR (p < 0.05) and decreased TAR were noted (p < 0.05). In GSD IX only increased TAR was observed (p < 0.05). IKH patient cohorts, both with and without treatment, presented CGM metrics similar to healthy individuals. ConclusionDespite dietary treatment, most liver GSD cohorts do not achieve CGM metrics comparable to healthy individuals. International recommendations on the use of CGM and clinical targets for CGM metrics in liver GSD patients are warranted, both for patient care and clinical trials.

Repurposing SGLT2 inhibitors: Treatment of renal proximal tubulopathy in Fanconi-Bickel syndrome with empagliflozin.

Renal proximal tubulopathy in Fanconi-Bickel syndrome is caused by impaired basolateral glucose transport via GLUT2 and consequently, intracellular accumulation of glucose and glycogen. SGLT2 inhibitors act on apical glucose reabsorption of renal proximal tubular cells. The purpose of this study was to retrospectively describe the first experiences with repurposing the SGLT2 inhibitor empagliflozin to treat the generalized tubulopathy in Fanconi-Bickel syndrome. A case series was conducted of seven persons from five families (five males, two females; three children, who were 14y5m, 2y9m, and 1y6m old) with genetically confirmed Fanconi-Bickel syndrome, off-label treated with empagliflozin. Median (range) age at start of empagliflozin was 27 years (1y6m - 61y) and duration of follow-up under empagliflozin treatment was 169 days (57-344). Under empagliflozin (up to 25 mg/d), biochemical parameters of tubular cell integrity (urinary N-acetyl-glucosaminidase) and/or tubular functions (including urinary α1-microglobulin) improved in all persons with Fanconi-Bickel syndrome, albeit to varying degrees. Clinically, supplementations (i.e., phosphate, alkali, carnitine, and alfacalcidol) could be completely discontinued in the three children, whereas results in the four adult patients were more variable and not as significant. Empagliflozin was well-tolerated and no symptomatic hypoglycemia was observed. In conclusion, SGLT2 inhibitors such as empagliflozin shift the metabolic block in Fanconi-Bickel syndrome, that is, they intervene specifically in the underlying pathophysiology and can thus attenuate renal proximal tubulopathy, especially when started in early childhood.

#1333 SGLT2 inhibitors as a treatment for Fanconi-Bickel syndrome: a case report

Abstract Background and Aims Fanconi-Bickel syndrome is an ultra-rare genetic disease characterized by SLC2A2 mutation encoding for the basolateral glucose transporter (GLUT2) in the proximal tubule of the nephron. This defective transport ultimately leads to accumulation of glycogen and dysfunction of proximal tubule cells. This manifests clinically as the renal Fanconi syndrome and eventually kidney failure. Systemic complications of proximal tubule injury include metabolic acidosis, bone demineralization and, for some not completely elucidated reasons, dysglycemia. Method We present the case of a 43-year-old man who was diagnosed with Fanconi-Bickel syndrome (homozygous splice site mutation in SLC2A2). He had a history of infantile-onset renal Fanconi syndrome, hypercalciuria and bilateral nephrolithiasis, osteoporosis, bilateral sensorineural deafness and non-insulin dependent type 2 diabetes. At referral the patient presented with CKD G2, non-anion gap metabolic acidosis, slightly elevated serum calcium, decreased serum phosphate, suppressed PTH and hypercalciuria (Table 1), despite oral supplementation of phosphate, bicarbonate and vitamin D. We hypothesized that SGLT2i in this patient may halt the progressive proximal tubule injury by preventive glucose uptake and help the management of diabetes. Results Fractional excretion of phosphate (FEPO4) and urinary retinol-binding protein (RBP)-creatinine ratio, two markers of proximal tubular injury, were stable after 2 months of SGLT2i therapy (Fig. 1). Conclusion To date, Fanconi-Bickel syndrome does not have a specific treatment. Standard of care includes supplements of fluids and electrolytes to counterbalance proximal tubular injury and management of complications such as diabetes. SGLT2i use has been described in a mouse model of another glycogen storage disease (GSD1b), whose underlying defect is different from that of Fanconi-Bickel but presents with a similar phenotype [2]. Data showed that gliflozins prevents glycogen accumulation and restores proximal tubule cells’ function. Using the same rationale, the administration of SGLT2i in adult patients with Fanconi-Bickel syndrome may prevent further proximal damage and slow the progression towards end-stage kidney disease. In conclusion, we hypothesize a potential benefit of SGLT2i in adult patients affected by Fanconi-Bickel syndrome.

Importance about use of high-throughput sequencing in pediatric: case report of a patient with Fanconi-Bickel syndrome

BackgroundFanconi-Bickel syndrome is characterized by hepatorenal disease caused by anomalous glycogen storage. It occurs due to variants in the SLC2A2 gene. We present a male patient of 2 years 7 months old, with failure to thrive, hepatomegaly, metabolic acidosis, hypophosphatemia, hypokalemia, hyperlactatemia.ResultsExome sequencing identified the homozygous pathogenic variant NM_000340.2(SLC2A2):c.1093 C > T (p.Arg365Ter), related with Fanconi-Bickel syndrome. He received treatment with bicarbonate, amlodipine, sodium citrate and citric acid solution, enalapril, alendronate and zolendronate, and nutritional management with uncooked cornstarch, resulting in an improvement of one standard deviation in weight and height.ConclusionsThe importance of knowing the etiology in rare genetic disease is essential, not only to determine individual and familial recurrence risk, but also to establish the treatment and prognosis; in this sense, access to a new genomic technology in low- and middle-income countries is essential to shorten the diagnostic odyssey.

Clinical, genetic profile and therapy evaluation of 11 Chinese pediatric patients with Fanconi-Bickel syndrome

BackgroundFanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder characterized by impaired glucose and galactose utilization as well as proximal renal tubular dysfunction.MethodsClinical, biochemical, genetic, treatment, and follow-up data for 11 pediatric patients with FBS were retrospectively analysed.ResultsHepatomegaly (10/11), short stature (10/11) and hypophosphataemic rickets (7/11) were the most common initial symptoms. At diagnosis, all patients had decreased fasting blood glucose (FBG), plasma bicarbonate (HCO3−) and serum phosphorus, as well as elevated liver transaminases, alkaline phosphatase (AKP) and proximal renal tubular dysfunction. Two infant patients were misdiagnosed with transient neonatal diabetes mellitus. After therapy with uncooked cornstarch and conventional rickets treatment, remission of hepatomegaly was observed in all patients, with significant improvements in pre-prandial blood glucose, liver transaminases, triglyceride, plasma HCO3− and AKP (p < 0.05). At the last follow-up, 5/7 patients with elevated AKP had nephrocalcinosis. The mean height standard deviation score (Ht SDS) of eight patients with regular treatment increased from − 4.1 to -3.5 (p = 0.02). Recombinant human growth hormone (rhGH) was administered to 4/9 patients, but their Ht SDS did not improve significantly (p = 0.13). Fourteen variants of the SLC2A2 gene were identified, with six being novel, among which one was recurrent: c.1217T > G (p.L406R) (allele frequency: 4/22, 18%). Patients with biallelic missense variants showed milder metabolic acidosis than those with null variants. Two of five patients from nonconsanguineous families with rare homozygous variations showed 5.3 Mb and 36.6 Mb of homozygosity surrounding the variants, respectively; a region of homozygosity (ROH) involving the entire chromosome 3 covering the SLC2A2 gene, suggesting uniparental disomy 3, was detected in one patient.ConclusionsEarly diagnosis of FBS is difficult due to the heterogeneity of initial symptoms. Although short stature is a major issue of treatment for FBS, rhGH is not recommended in FBS patients who have normal GH stimulation tests. Patients with biallelic null variants may require alkali supplementation since urine bicarbonate loss is genetically related. ROH is a mechanism for rare homozygous variants of FBS in nonconsanguineous families.

“A Complex Conundrum”- Fanconi-Bickel Syndrome

Fanconi-Bickel Syndrome (FBS) is a rare form of Glycogen Storage Disease (GSD) type 11 characterised by massive hepatomegaly due to the buildup of glycogen and severe hypophosphatemic rickets due to a proximal renal tubular dysfunction. Since 1940, it has been initially known as hepatorenal glycogenesis with proximal renal tubular dysfunction. It is due to a pathogenic mutation of the GLUT-2 (glucose transporter) gene. Herein, present case report a young toddler who is the firstborn of 3rd-degree consanguinity, presented with rickets, recurrent respiratory tract infections, and hepatomegaly, and was subsequently diagnosed with FBS with the help of genetic studies, showing a mutation in the GLUT-2 gene. With less than 200 cases reported so far, this child represents a unique case with recurrent respiratory infections and developmental delay as presentations along with rachitic features.

Fanconi-Bickel Syndrome: A Rare Etiology of Hypophosphatemic Rickets

Fanconi-Bickel syndrome (FBS) is a rare type of glycogen storage disease (GSD). Usual presentations of this condition are hepatomegaly, nephropathy, postprandial hyperglycemia, fasting hypoglycemia, developmental delay and growth retardation. An investigation shows rachitic changes with calcinuria, phosphaturia, glycosuria, and metabolic acidosis. Liver biopsy shows features of GSD and whole exome sequencing shows solute carrier family 2, facilitated glucose transporter member 1 gene mutation which encodes glucose transporter (GLUT2). In this study, we present the case of a child who had presented with abdominal distention and rachitic changes and finally diagnosed as FBS. This case report aims to show that hepatomegaly with rachitic features may reveal a rare diagnosis of FBS.

The SGLT2 inhibitor dapagliflozin improves kidney function in glycogen storage disease XI.

Glycogen storage disease XI, also known as Fanconi-Bickel syndrome (FBS), is a rare autosomal recessive disorder caused by mutations in the SLC2A2 gene that encodes the glucose-facilitated transporter type 2 (GLUT2). Patients develop a life-threatening renal proximal tubule dysfunction for which no treatment is available apart from electrolyte replacement. To investigate the renal pathogenesis of FBS, SLC2A2 expression was ablated in mouse kidney and HK-2 proximal tubule cells. GLUT2Pax8Cre+ mice developed time-dependent glycogen accumulation in proximal tubule cells and recapitulated the renal Fanconi phenotype seen in patients. In vitro suppression of GLUT2 impaired lysosomal autophagy as shown by transcriptomic and biochemical analysis. However, this effect was reversed by exposure to a low glucose concentration, suggesting that GLUT2 facilitates the homeostasis of key cellular pathways in proximal tubule cells by preventing glucose toxicity. To investigate whether targeting proximal tubule glucose influx can limit glycogen accumulation and correct symptoms in vivo, we treated mice with the selective SGLT2 inhibitor dapagliflozin. Dapagliflozin reduced glycogen accumulation and improved metabolic acidosis and phosphaturia in the animals by normalizing the expression of Napi2a and NHE3 transporters. In addition, in a patient with FBS, dapagliflozin was safe, improved serum potassium and phosphate concentrations, and reduced glycogen content in urinary shed cells. Overall, this study provides proof of concept for dapagliflozin as a potentially suitable therapy for FBS.

SGLT2 Inhibitors as a Treatment for Fanconi-Bickel Syndrome: A Case Report

SGLT2 Inhibitors as a Treatment for Fanconi-Bickel Syndrome: A Case Report

Clinical Features and Genetic Sequencing of Children with Fanconi-Bickel Syndrome.

The present paper reports 10 patients (9 families) with Fanconi-Bickel syndrome managed during 2010-2021. Patients presented with polyuria, polydipsia, hepatomegaly, rickets, and stunting at a median of 5 (3, 7.3) mo; one had transient neonatal diabetes. Glucosuria, generalized aminoaciduria, β2-microglobinuria, urinary phosphate wasting, and hypercalciuria were present in all patients; 3 patients had nephrocalcinosis. Other metabolic abnormalities included hypertriglyceridemia (n = 5/6), fasting hypoglycemia (n = 5/8), and postprandial hyperglycemia (n = 3/6). Genetic analysis showed 7 homozygous or compound heterozygous variants in SLC2A2. A pathogenic variant c.952G>A, common to 4 patients (3 families), might be a potential hotspot. At a median follow-up of 43 mo, 4 patients died at a median of 25 mo; short stature persisted in all except one patient who showed catch-up growth with uncooked corn-starch diet. The present findings suggest that the Fanconi-Bickel syndrome has a severe phenotype with an unsatisfactory outcome. A high index of suspicion for diagnosis and efforts for facilitation of dietary therapy are necessary.

An induced pluripotent stem cell line derived from a patient with neonatal diabetes and Fanconi-Bickel syndrome caused by a homozygous mutation in the SLC2A2 gene

An induced pluripotent stem cell line derived from a patient with neonatal diabetes and Fanconi-Bickel syndrome caused by a homozygous mutation in the SLC2A2 gene

Understanding the Role of GLUT2 in Dysglycemia Associated with Fanconi-Bickel Syndrome.

Fanconi–Bickel Syndrome (FBS) is a rare disorder of carbohydrate metabolism that is characterized by the accumulation of glycogen mainly in the liver. It is inherited in an autosomal recessive manner due to mutations in the SLC2A2 gene. SLC2A2 encodes for the glucose transporter GLUT2 and is expressed in tissues that are involved in glucose homeostasis. The molecular mechanisms of dysglycemia in FBS are still not clearly understood. In this study, we report two cases of FBS with classical phenotypes of FBS associated with dysglycemia. Genomic DNA was extracted and analyzed by whole-genome and Sanger sequencing, and patient PBMCs were used for molecular analysis. One patient had an exonic SLC2A2 mutation (c.1093C>T in exon 9, R365X), while the other patient had a novel intronic SLC2A2 mutation (c.613-7T>G). Surprisingly, the exonic mutation resulted in the overexpression of dysfunctional GLUT2, resulting in the dysregulated expression of other glucose transporters. The intronic mutation did not affect the coding sequence of GLUT2, its expression, or glucose transport activity. However, it was associated with the expression of miRNAs correlated with type 1 diabetes mellitus, with a particular significant overexpression of hsa-miR-29a-3p implicated in insulin production and secretion. Our findings suggest that SLC2A2 mutations cause dysglycemia in FBS either by a direct effect on GLUT2 expression and/or activity or, indirectly, by the dysregulated expression of miRNAs implicated in glucose homeostasis.

Understanding the Mechanism of Dysglycemia in a Fanconi-Bickel Syndrome Patient.

Fanconi–Bickel Syndrome (FBS) is a rare disorder of carbohydrate metabolism that is characterized mainly by the accumulation of glycogen in the liver and kidney. It is inherited as an autosomal recessive disorder caused by mutations in the SLC2A2 gene, which encodes for GLUT2. Patients with FBS have dysglycemia but the molecular mechanisms of dysglycemia are still not clearly understood. Therefore, we aimed to understand the underlying molecular mechanisms of dysglycemia in a patient with FBS. Genomic DNA was isolated from a peripheral blood sample and analyzed by whole genome and Sanger sequencing. CRISPR-Cas9 was used to introduce a mutation that mimics the patient’s mutation in a human kidney cell line expressing GLUT2 (HEK293T). Mutant cells were used for molecular analysis to investigate the effects of the mutation on the expression and function of GLUT2, as well as the expression of other genes implicated in dysglycemia. The patient was found to have a homozygous nonsense mutation (c.901C>T, R301X) in the SLC2A2 gene. CRISPR-Cas9 successfully mimicked the patient’s mutation in HEK293T cells. The mutant cells showed overexpression of a dysfunctional GLUT2 protein, resulting in reduced glucose release activity and enhanced intracellular glucose accumulation. In addition, other glucose transporters (SGLT1 and SGLT2 in the kidney) were found to be induced in the mutant cells. These findings suggest the last loops (loops 9-12) of GLUT2 are essential for glucose transport activity and indicate that GLUT2 dysfunction is associated with dysglycemia in FBS.

Pediatric metanephric adenoma with Fanconi-Bickel syndrome: a case report and review of literature.

BackgroundMetanephric adenoma (MA) is a rare benign renal tumor that resembles renal cell carcinoma and Wilms’ tumor in radiological as well as pathological appearance. It can present at any age or gender, and it is extremely rare in the pediatric age group with less than 50 reported cases. Fanconi–Bickel syndrome (FBS) is a rare autosomal recessive disorder of carbohydrate metabolism. Herein, we report a rare incidence of MA in a boy with a genetically confirmed FBS who underwent a nephron-sparing surgery.Case presentationA 21-month-old boy was referred to the pediatric urology clinic for further evaluation of an incidentally discovered left renal mass. His laboratory investigations showed normal renal function, hypophosphatemia, high blood glucose level, markedly elevated serum alkaline phosphatase, and low serum vitamin D. Blood picture showed signs of polycythemia and urinalysis showed glucosuria and aminoaciduria. Genetic testing was positive for Fanconi–Bickel syndrome. Radiological investigations were carried out with abdominal ultrasound and computerized tomography (CT) with intravenous contrast documented a sharply marginated peripheral hypoechoic hypovascular homogeneously enhancing mass at the upper pole of the left kidney measuring 2.0 × 1.8 × 2.0 cm. The child was admitted and started on supportive treatment until his medical condition was stabilized, then underwent elective open left partial nephrectomy via a left upper transverse abdominal transperitoneal incision. The excised renal mass was sent for histopathological assessment and was found to be a tumor composed of tightly packed tubules with no mitotic figures or necrosis and scanty cytoplasm consistent with MA. After good hydration and tumor resection, his polycythemia gradually improved. The patient was discharged home in a good condition with his proper replacement therapies. His follow-up abdominal ultrasound after 12 months showed no signs of recurrence.ConclusionsMetanephric adenoma is extremely rare in the pediatric age group, especially in those who have a FBS. The only way to diagnose and treat this tumor is by surgical resection as most patients are asymptomatic. A nephron-sparing surgery is better for this age group in which the future renal function is considered.

In-silico analysis of phylogenetic relationship and potentially damaging nsSNPs in human SLC2A2 gene

Transport of glucose across the eukaryotic cell membranes is carried out by members of the glucose transporter (GLUT) family which is mainly divided into three classes (I, II and III) on the basis of phylogenetic relationship. In humans, one member of Class I called GLUT2 is encoded by solute carrier family 2, facilitated glucose transporter member 2 (SLC2A2) gene located on third chromosome. Protein mediatedglucosemovement acrosscell membranes is made possible through GLUT2 that is atrans-membrane carrierprotein. It regulates the entry of glucose and secretion of insulin in the pancreatic cell. It has three isoforms and the longest isoform consists of 524 amino acid. There are 13 extracellular, 12 transmembrane and 5 cytoplasmic domains in human GLUT2. The risk of Fanconi-Bickel syndrome (FBS), diabetes, breast cancer (BC) and Alzheimer disease (AD) is associated with improper functioning of GLUT2. The most frequent form of genetic changes is single nucleotide polymorphism (SNPs). Non synonymous SNPs (nsSNPs) can result in alterations of amino acids and subsequent changes in phenotype. In this study, in-silico analysis was done to find phylogenetic relationship of human GLUT2 protein and possible deleterious effect of nsSNPs of its coding region. Clustal Omega was used to make phylogenetic tree. SIFT, PolyPhen, PROVEAN and SNPeffect were used to predict deleterious or tolerated SNPs. 167 nsSNPs were predicted to be damaging by SIFT, 65 to be possibly damaging and 77 to be probably damaging by PolyPhen. PROVEAN predicted 162 nsSNPs to be neutral and 138 to be deleterious. 101 SNPs were found to be damaging by three algorithms; SIFT, PolyPhen and PROVEAN.

Potential Role of Glucose Transporters in Glucose Homeostasis: a Narrative Review

Background: The GLUT2 (glucose transporter 2) is a glucose sensitive receptor gene found in the liver, pancreas, and sometimes in the CNS. The experiments conducted on the genetically modified mice revealed their role in the different regulatory mechanisms.&#x0D; Objective: The current narrative review aims to elucidate the role of GLUT2 in glucose homeostasis.&#x0D; Methods: The recent related articles were reviewed with the help of different databases including PubMed, Google Scholar, Springer link, and Science direct. To ensure the credibility of data, articles published only in indexed journals were considered.&#x0D; Results: In the liver (hepatocytes), it’s reported that there is an unsuspected glucose pathway (output) that is dependent on the membrane mechanism is in progress. In humans, due to the mutation in the GLUT2 gene, there is a syndrome known as “Fanconi–Bickel syndrome” which dictates a glycogen storage disease type 11 disease characterized by kidney and liver disorders.&#x0D; Conclusion: It is concluded from the genome-wide association studies that the genetic mutations in GLUT2 result in an increased risk of high cholesterol, cardiovascular diseases (CVDs), and fasting hyperglycemia.

An induced pluripotent stem cell line derived from a patient with neonatal diabetes and Fanconi-Bickel syndrome caused by a homozygous mutation in the SLC2A2 gene

Recessive mutations in the glucose transporter gene SLC2A2 (GLUT2) lead to permanent neonatal diabetes (PNDM) and Fanconi Bickel Syndrome (FBS). Here, we generated an induced pluripotent stem cell (iPSC) line, QBRIi012-A, from a 24-month-old boy with FBS and PNDM due to homozygous nonsense mutation in the SLC2A2 gene (c.901C > T). The QBRIi012-A was fully characterized using different approaches. The cell line showed normal karyotype and was able to differentiate into the three germ layers in vitro. This iPSC line provides a novel human cell model to understand the pathophysiology of FBS and diabetes associated with SLC2A2 defects.

Next-generation sequencing in children of West India with suspected inherited tubulopathies

Background: The renal tubules maintain homeostasis through an array of proteins coded by multiple genes, which directly or indirectly transport water and solutes in the tubules. Malfunction of these transport proteins leads to inherited tubulopathies. Objective: The objective of the study was to analyze the clinical utility of next-generation sequencing (NGS) in the diagnosis and management of children with tubulopathies. Materials and Methods: This retrospective study was conducted in a tertiary care nephrology center in West India between September 2016 and September 2020. All children ?18 years with suspected inherited tubulopathy, where an NGS was sent, were included. Clinical exome sequencing (CES) covering 6670 genes was done in 14 children. CES included 73 tubulopathy genes. The test result was interpreted as per American College of Medical Genetics classification: No pathogenic variant, variant of unknown significance (VUS), and likely pathogenic and pathogenic variant. Results: The median age (IQR) of the cohort at the onset of disease was 18 months (4–65). History of consanguinity was present in 2 children (14.2%). Five children (35.7%) had Fanconi syndrome, two had distal renal tubular acidosis (d-RTA), two had Bartter/Gitelman syndrome, two had rickets, two had nephrocalcinosis, and one had low-molecular-weight proteinuria. Nine children (64%) had pathogenic variants detected in eight genes: ATP6V0A4, CTNS1, FAH1, PHEX, SLC12A1, SLC4A1, SLCA2, and CLDN 16. Five (35.7%) were novel variants. Two children had three VUS in FAT1, EYA1, and KCNJ1 gene. Three children (21.4%) had no genetic variant. Bartter syndrome type 1 and d-RTA were the most common genetic diagnoses with two patients each. Other diagnoses were tyrosinemia type 1, nephropathic cystinosis, Fanconi Bickel syndrome, X-linked hypophosphatemic rickets, and familial hypomagnesemia, hypercalciuria, and nephrocalcinosis in one each. Conclusion: The yield of NGS in children with tubulopathy was remarkably high. NGS was useful in the diagnosis and management in these children.

Etiologic distribution and clinical characteristics of pediatric diabetes in 276 children and adolescents with diabetes at a single academic center

BackgroundThe prevalence of monogenic diabetes is estimated to be 1.1–6.3% of patients with diabetes mellitus (DM) in Europe. The overlapping clinical features of various forms of diabetes make differential diagnosis challenging. Therefore, this study investigated the etiologic distribution and clinical characteristics of pediatric diabetes, including monogenic diabetes, who presented at a single tertiary center over the last 20 years.MethodsThis study included 276 consecutive patients with DM diagnosed before 18 years of age from January 2000 to December 2019 in Korea. Clinical features, biochemical findings, β-cell autoantibodies, and molecular characteristics were reviewed retrospectively.ResultsOf the 276 patients, 206 patients (74.6%), 49 patients (17.8%), and 21 patients (7.6%) were diagnosed with type 1 DM, type 2 DM, and clinically suspected monogenic diabetes, respectively. Among 21 patients suspected to have monogenic diabetes, 8 patients had clinical maturity-onset diabetes of the young (MODY), and the remaining 13 patients had other types of monogenic diabetes. Among them, genetic etiologies were identified in 14 patients (5.1%) from 13 families, which included MODY 5, transient neonatal DM, developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, Wolfram syndrome, Donohue syndrome, immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, Fanconi-Bickel syndrome, Wolcott-Rallison syndrome, cystic fibrosis-related diabetes, and maternally inherited diabetes and deafness.ConclusionsGenetically confirmed monogenic diabetes accounted for 5.1% of patients evaluated at a single tertiary center over 20-year period. Based on the findings for our sample, the frequency of mutations in the major genes of MODY appears to be low among pediatric patients in Korea. It is critical to identify the genetic cause of DM to provide appropriate therapeutic options and genetic counseling.