Diagnosis, Treatment, and Outcomes in Children With Congenital Nephrogenic Diabetes Insipidus: A Pediatric Nephrology Research Consortium Study

Congenital nephrogenic diabetes insipidus treated with acetazolamide

Congenital nephrogenic diabetes insipidus (CNDI) is a rare disorder. The condition is characterised by an inability of distal nephron segments to respond to normal or raised concentrations of serum antidiuretic hormone. In this report, we describe the case of a 13-year-old male known with CNDI who experienced a pedestrian vehicle accident leading to coma following a head injury. Intra-operatively, severe hypernatraemia and polyuria were observed. Following an inadequate response to conventional therapy, acetazolamide was prescribed resulting in an immediate response to therapy. To the best of our knowledge, acetazolamide has not been previously documented as a therapeutic option for CNDI. Additional research is necessary before considering the recommendation of acetazolamide for cases of NDI that do not respond adequately to conventional treatments.

Is mild dehydration a risk for progression of childhood chronic kidney disease?

Children with chronic kidney disease (CKD) can have an inherent vulnerability to dehydration. Younger children are unable to freely access water, and CKD aetiology and stage can associate with reduced kidney concentrating capacity, which can also impact risk. This article aims to review the risk factors and consequences of mild dehydration and underhydration in CKD, with a particular focus on evidence for risk of CKD progression. We discuss that assessment of dehydration in the CKD population is more challenging than in the healthy population, thus complicating the definition of adequate hydration and clinical research in this field. We review pathophysiologic studies that suggest mild dehydration and underhydration may cause hyperfiltration injury and impact renal function, with arginine vasopressin as a key mediator. Randomised controlled trials in adults have not shown an impact of improved hydration in CKD outcomes, but more vulnerable populations with baseline low fluid intake or poor kidney concentrating capacity need to be studied. There is little published data on the frequency of dehydration, and risk of complications, acute or chronic, in children with CKD. Despite conflicting evidence and the need for more research, we propose that paediatric CKD management should routinely include an assessment of individual dehydration risk along with a treatment plan, and we provide a framework that could be used in outpatient settings.

Genetic basis of nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus is defined as an inability to concentrate urine due to a complete or partial alteration of the renal tubular response to arginine vasopressin hormone, resulting in excessive diluted urine excretion. Hereditary forms are caused by molecular defects in the genes encoding either of the two main renal effectors of the arginine vasopressin pathway: the AVPR2 gene, which encodes for the type 2 vasopressin receptor, or the AQP2 gene, which encodes for the water channel aquaporin-2. About 90% of cases of nephrogenic diabetes insipidus result from loss-of-function variants in the AVPR2 gene, which are inherited in a X-linked recessive manner. The remaining 10% of cases result from loss-of-function variants in the AQP2 gene, which can be inherited in either a recessive or a dominant manner. The main symptoms of the disease are polyuria, chronic dehydration and hypernatremia. These symptoms usually occur in the first year of life, although some patients present later. Diagnosis is based on abnormal response in urinary osmolality after water restriction and/or administration of exogenous vasopressin. Treatment involves ensuring adequate water intake on demand, possibly combined with thiazide diuretics, non-steroidal anti-inflammatory drugs, and a low-salt and protein diet. In this review, we provide an update on current understanding of the molecular basis of inherited nephrogenic insipidus diabetes.

Congenital nephrogenic diabetes insipidus arginine vasopressin receptor 2 gene mutation at new site: A case report

BACKGROUND

Congenital nephrogenic diabetes insipidus (CNDI) is a rare hereditary disorder. It is associated with mutations in the arginine vasopressin receptor 2 (AVPR2) gene and aquaporin 2 (AQP2) gene, and approximately 270 different mutation sites have been reported for AVPR2. Therefore, new mutations and new manifestations are crucial to complement the clinical deficiencies in the diagnosis of this disease. We report a case of a novel AVPR2 gene mutation locus and a new clinical mani-festation.

CASE SUMMARY

We describe the case of a 48-d-old boy who presented with recurrent fever and diarrhea 5 d after birth. Laboratory tests showed electrolyte disturbances and low urine specific gravity, and imaging tests showed no abnormalities. Genetic testing revealed a novel X-linked recessive missense mutation, c.283 (exon 2) C>T (p.P95S). This mutation results in the substitution of a proline residue with a serine residue in the AVPR2 protein sequence. The diagnosis of CNDI was confirmed based on the AVPR2 gene mutation. The treatment strategy for this patient was divided into two stages, including physical cooling supplemented with appropriate amounts of water in the early stage and oral hydrochlorothia-zide (1-2 mg/kg) after a clear diagnosis. After follow-up of one and a half years, the patient gradually improved.

CONCLUSION

AVPR2 gene mutations in new loci and new clinical symptoms help clinicians understand this disease and shorten the diagnosis cycle.

Fluid management in hospitalized pediatric patients

The proper use of intravenous fluids has likely been responsible for saving more lives than any other group of substances. Proper use includes prescribing an appropriate electrolyte and carbohydrate solution, at a calculated rate or volume, for the right child, at the right time. Forming intravenous fluid plans for hospitalized children requires an understanding of water and electrolyte physiology in healthy children and how different pathology deviates from the norm. This review highlights fluid management in several disease types, including liver disease, diabetic ketoacidosis, syndrome of inappropriate antidiuretic hormone, diabetes insipidus, kidney disease, and intestinal failure as well as in those with nonphysiologic fluid losses. For each disease, the review discusses specific considerations, evaluations, and management strategies to consider when customizing intravenous fluid plans. Ultimately, all hospitalized children should receive an individualized fluid plan with recurrent evaluations and fluid modifications to provide optimal care.

Nephrogenic diabetes insipidus: a comprehensive overview

Nephrogenic diabetes insipidus (NDI) is characterized by the inability to concentrate urine that results in polyuria and polydipsia, despite having normal or elevated plasma concentrations of arginine vasopressin (AVP). In this study, we review the clinical aspects and diagnosis of NDI, the various etiologies, current treatment options and potential future developments. NDI has different clinical manifestations and approaches according to the etiology. Hereditary forms of NDI are mainly caused by mutations in the genes that encode key proteins in the AVP signaling pathway, while acquired causes are normally associated with specific drug exposure, especially lithium, and hydroelectrolytic disorders. Clinical manifestations of the disease vary according to the degree of dehydration and hyperosmolality, being worse when renal water losses cannot be properly compensated by fluid intake. Regarding the diagnosis of NDI, it is important to consider the symptoms of the patient and the diagnostic tests, including the water deprivation test and the baseline plasma copeptin measurement, a stable surrogate biomarker of AVP release. Without proper treatment, patients may developcomplications leading to high morbidity and mortality, such as severe dehydration and hypernatremia. In that sense, the treatment of NDI consists in decreasing the urine output, while allowing appropriate fluid balance, normonatremia, and ensuring an acceptable quality of life. Therefore, therapeutic options include nonpharmacological interventions, including sufficient water intake and a low-sodium diet, and pharmacological treatment. The main medications used for NDI are thiazide diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), and amiloride, used isolated or in combination.

Clinical, Genetic and Functional Characterization of a Novel AVPR2 Missense Mutation in a Woman with X-Linked Recessive Nephrogenic Diabetes Insipidus

Nephrogenic diabetes insipidus (NDI) is a rare disorder characterized by renal unresponsiveness to the hormone vasopressin, leading to excretion of large volumes of diluted urine. Mutations in the arginine vasopressin receptor-2 (AVPR2) gene cause congenital NDI and have an X-linked recessive inheritance. The disorder affects almost exclusively male family members, but female carriers occasionally present partial phenotypes due to skewed inactivation of the X-chromosome. Here, we report a rare case of a woman affected with X-linked recessive NDI, presenting an average urinary output of 12 L/day. Clinical and biochemical studies showed incomplete responses to water deprivation and vasopressin stimulation tests. Genetic analyses revealed a novel heterozygous missense mutation (c.493G > C, p.Ala165Pro) in the AVPR2 gene. Using a combination of in-silico protein modeling with human cellular models and molecular phenotyping, we provide functional evidence for phenotypic effects. The mutation destabilizes the helical structure of the AVPR2 transmembrane domains and disrupts its plasma membrane localization and downstream intracellular signaling pathways upon activation with its agonist vasopressin. These defects lead to deficient aquaporin 2 (AQP2) membrane translocation, explaining the inability to concentrate urine in this patient.

The usefulness of copeptin for the diagnosis of nephrogenic diabetes insipidus in infancy: a case report

OBJECTIVES

We report a case of an infant with nephrogenic diabetes insipidus (NDI) diagnosed by the measurement of serum copeptin. There is only one study that previously evaluated the use of copeptin measurement in a pediatric patient.

CASE PRESENTATION

We present a 10-month-old child with polyuria-polydipsia syndrome (PPS) and hypernatremia that could not support water restriction due to increased risk of dehydration and worsening of his condition. Therefore, plasma measurement of copeptin allowed the diagnosis of NDI.

CONCLUSIONS

The water deprivation test (WDT) is considered the gold standard for diagnosis in PPS. However, WDT has serious limitations regarding its interpretation. Furthermore, the WDT can cause dehydration and hypernatremia, especially in young children. Therefore, the measurement of plasma copeptin seems to be a promising method to perform an earlier, safer, and accurate investigation of PPS. Up to now, our study is the second to report the usefulness of copeptin in children.

Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Bartter and Gitelman Syndromes: A Primer for Clinicians

Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies.

Nephrogenic diabetes insipidus in children (Review)

Nephrogenic diabetes insipidus (NDI) is characterized by impaired urinary concentrating ability, despite normal or elevated plasma concentrations of the antidiuretic hormone, arginine vasopressin (AVP). NDI can be inherited or acquired. NDI can result from genetic abnormalities, such as mutations in the vasopressin V2 receptor (AVPR2) or the aquaporin-2 (AQP2) water channel, or acquired causes, such as chronic lithium therapy. Congenital NDI is a rare condition. Mutations in AVPR2 are responsible for approximately 90% of patients with congenital NDI, and they have an X-linked pattern of inheritance. In approximately 10% of patients, congenital NDI has an autosomal recessive or dominant pattern of inheritance with mutations in the AQP2 gene. In 2% of cases, the genetic cause is unknown. The main symptoms at presentation include growth retardation, vomiting or feeding concerns, polyuria plus polydipsia, and dehydration. Without treatment, most patients fail to grow normally, and present with associated constipation, urological complication, megacystis, trabeculated bladder, hydroureter, hydronephrosis, and mental retardation. Treatment of NDI consist of sufficient water intake, low-sodium diet, diuretic thiazide, sometimes in combination with a cyclooxygenase (COX) inhibitor (indomethacin) or nonsteroidal anti-inflammatory drugs (NSAIDs), or hydrochlorothiazide in combination with amiloride. Some authors note a generally favorable long-term outcome and an apparent loss of efficacy of medical treatment during school age.

Vasopressin-Dependent Disorders: What Is New in Children?

Arginine vasopressin (AVP)-mediated osmoregulatory disorders, such as diabetes insipidus (DI) and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are common in the differential diagnosis for children with hypo- and hypernatremia and require timely recognition and treatment. DI is caused by a failure to concentrate urine secondary to impaired production of or response to AVP, resulting in hypernatremia. Newer methods of diagnosing DI include measuring copeptin levels; copeptin is AVP's chaperone protein and serves as a surrogate biomarker of AVP secretion. Intraoperative copeptin levels may also help predict the risk for developing DI after neurosurgical procedures. Copeptin levels hold diagnostic promise in other pediatric conditions, too. Recently, expanded genotype and phenotype correlations in inherited DI disorders have been described and may better predict the clinical course in affected children and infants. Similarly, newer formulations of synthetic AVP may improve pediatric DI treatment. In contrast to DI, SIADH, characterized by inappropriate AVP secretion, commonly leads to severe hyponatremia. Contemporary methods aid clinicians in distinguishing SIADH from other hyponatremic conditions, particularly cerebral salt wasting. Further research on the efficacy of therapies for pediatric SIADH is needed, although some adult treatments hold promise for pediatrics. Lastly, expansion of home point-of-care sodium testing may transform management of SIADH and DI in children. In this article, we review recent developments in the understanding of pathophysiology, diagnostic workup, and treatment of better outcomes and quality of life for children with these challenging disorders.

Integrating Population Variants and Protein Structural Analysis to Improve Clinical Genetic Diagnosis and Treatment in Nephrogenic Diabetes Insipidus

Congenital nephrogenic diabetes insipidus (NDI) is a rare genetic disorder characterized by renal inability to concentrate urine. We utilized a multicenter strategy to investigate the genotype and phenotype in a cohort of Chinese children clinically diagnosed with NDI from 2014 to 2019. Ten boys from nine families were identified with mutations in AVPR2 or AQP2 along with dehydration, polyuria-polydipsia, and severe hypernatremia. Genetic screening confirmed the diagnosis of seven additional relatives with partial or subclinical NDI. Protein structural analysis revealed a notable clustering of diagnostic mutations in the transmembrane region of AVPR2 and an enrichment of diagnostic mutations in the C-terminal region of AQP2. The pathogenic variants are significantly more likely to be located inside the domain compared with population variants. Through the structural analysis and in silico prediction, the eight mutations identified in this study were presumed to be disease-causing. The most common treatments were thiazide diuretics and non-steroidal anti-inflammatory drugs (NSAIDs). Emergency treatment for hypernatremia dehydration in neonates should not use isotonic saline as a rehydration fluid. Genetic analysis presumably confirmed the diagnosis of NDI in each patient in our study. We outlined methods for the early identification of NDI through phenotype and genotype, and outlined optimized treatment strategies.

Congenital nephrogenic diabetes insipidus due to the mutation in AVPR2 (c.541C>T) in a neonate: A case report

BACKGROUND

Congenital nephrogenic diabetes insipidus (CNDI) is a rare hereditary renal disorder that is caused by mutations in AVPR2 or aquaporin 2 (AQP2). Up to now, there are few reports about CNDI in neonates. Early clinical manifestations of CNDI in neonates are atypical. A lack of understanding of the disease by clinicians causes frequent misdiagnoses or missed diagnoses, which may result in failure to administer treatments in time and ultimately leads to severe complications. In this study, clinical data of a case of AVPR2 gene mutation-induced CNDI, which was confirmed by genetic testing, were retrospectively analyzed to improve our understanding of this disease.

CASE SUMMARY

On February 1, 2020, a male neonate was hospitalized 17 d after birth due to a 7 d period of pyrexia. The patient’s symptoms included recurrent pyrexia, hypernatremia and hyperchloremia, which were difficult to treat. The patient was fed on demand, and water was additionally provided between milk intakes. A combination treatment of hydrochlorothiazide and amiloride was administered. After the treatment, body temperature and electrolyte levels returned to normal, the volume of urine was significantly reduced and the patient was subsequently discharged. Genetic tests confirmed that the patient carried the AVPR2 gene missense mutation c.541C>T (P.R181C), and the patient’s mother carried a heterozygous mutation at the same locus. After clinical treatment with a combination of hydrochlorothiazide and amiloride, the body temperature and electrolyte levels returned to normal. Up until the most recent follow-up examination, normal body temperature, electrolyte levels and growth and development were observed.

CONCLUSION

CNDI in the neonatal period is rare, and its clinical manifestations are unspecific with some patients merely showing recurrent fever and electrolyte disturbance. Genetic testing of AVPR2 and AQP2 can be used for screening and genetic diagnosis of CNDI.

Treatment and long-term outcome in primary nephrogenic diabetes insipidus

BACKGROUND

Primary nephrogenic diabetes insipidus (NDI) is a rare disorder and little is known about treatment practices and long-term outcome.

METHODS

Paediatric and adult nephrologists contacted through European professional organizations entered data in an online form.

RESULTS

Data were collected on 315 patients (22 countries, male 84%, adults 35%). Mutation testing had been performed in 270 (86%); pathogenic variants were identified in 258 (96%). The median (range) age at diagnosis was 0.6 (0.0-60) years and at last follow-up 14.0 (0.1-70) years. In adults, height was normal with a mean (standard deviation) score of -0.39 (±1.0), yet there was increased prevalence of obesity (body mass index >30 kg/m2; 41% versus 16% European average; P < 0.001). There was also increased prevalence of chronic kidney disease (CKD) Stage ≥2 in children (32%) and adults (48%). Evidence of flow uropathy was present in 38%. A higher proportion of children than adults (85% versus 54%; P < 0.001) received medications to reduce urine output. Patients ≥25 years were less likely to have a university degree than the European average (21% versus 35%; P = 0.003) but full-time employment was similar. Mental health problems, predominantly attention-deficit hyperactivity disorder (16%), were reported in 36% of patients.

CONCLUSION

This large NDI cohort shows an overall favourable outcome with normal adult height and only mild to moderate CKD in most. Yet, while full-time employment was similar to the European average, educational achievement was lower, and more than half had urological and/or mental health problems.