Best Practice of Peritoneal Dialysis-Associated Gram-Negative Peritonitis in Children: Insights From the International Pediatric Peritoneal Dialysis Network Registry.

Introduction: Gram-negative peritonitis (GNP) is associated with significant morbidity in children receiving long-term peritoneal dialysis (PD) and current treatment recommendations are based on limited data. Methods: Analysis of 379 GNP episodes in 308 children (median age 6.9 years, interquartile range [IQR]: 3.0-13.6) from 45 centers in 28 countries reported to the International Pediatric Peritoneal Dialysis Network registry between 2011 and 2023. Results: Overall, 74% of episodes responded well to empiric therapy and full functional recovery (FFR) was achieved in 82% of cases. In vitro bacterial susceptibility to empiric antibiotics and lack of severe abdominal pain at onset were associated with a good initial response. Risk factors for failure to achieve FFR included severe abdominal pain at onset and at 60 to 72 hours from treatment initiation (odds ratio [OR]: 3.81, 95% confidence interval [CI]: 2.01-7.2 and OR: 3.94, 95% CI: 1.06-14.67, respectively), Pseudomonas spp. etiology (OR: 1.73, 95% CI: 1.71-4.21]) and in vitro bacterial resistance to empiric antibiotics (OR: 2.40, 95% CI: 1.21-4.79); the risk was lower with the use of monotherapy as definitive treatment (OR: 0.40, 95% CI: 0.21-0.77). Multivariate analysis showed no benefit of dual antibiotic therapy for treatment of Pseudomonas peritonitis after adjustment for age, presenting symptomatology, 60 to 72-hour treatment response, and treatment duration. Monotherapy with cefazolin in susceptible Enterobacterales peritonitis resulted in a similar FFR rate (91% vs. 93%) as treatment with ceftazidime or cefepime monotherapy. Conclusion: Detailed microbiological assessment, consisting of patient-specific and center-specific antimicrobial susceptibility data, should guide empiric treatment. Treatment "deescalation" with the use of monotherapy and narrow spectrum antibiotics according to susceptibility data is not associated with inferior outcomes and should be advocated in the context of emerging bacterial resistance.

Correction: Spanò et al. Effect of Dual-Task Motor-Cognitive Training in Preventing Falls in Vulnerable Elderly Cerebrovascular Patients: A Pilot Study. Brain Sci. 2022, 12, 168.

In the original publication [...].

A Rare De Novo Mutation in the TRIM8 Gene in a 17-Year-Old Boy with Steroid-Resistant Nephrotic Syndrome: Case Report.

Idiopathic nephrotic syndrome is the most common chronic glomerular disease in children. Treatment with steroids is usually successful; however, in a small percentage of patients, steroid resistance is observed. The most frequent histologic kidney feature of steroid-resistant nephrotic syndrome (SRNS) is focal segmental glomerulosclerosis (FSGS). Genetic testing has become a valuable diagnostic tool in defining the etiology of SRNS, leading to the identification of a genetic cause. The TRIM8 gene is expressed in various tissues, including kidney cells and the central nervous system (CNS). An association between a mutation in the TRIM8 gene and an early onset of FSGS has been proposed but is not well described. We present a 17-year-old boy with epilepsy, early mild developmental delay, a low IgG serum level, and proteinuria, secondary to FSGS. A Next-Generation Sequencing (NGS)-based analysis revealed a heterozygous de novo pathogenic variant in the TRIM8 gene (c.1200C>G, p.Tyr400Ter). TRIM8 gene sequencing should be considered in individuals with early onset of FSGS, particularly accompanied by symptoms of cortical dysfunction, such as epilepsy and intellectual disability.

Development of a tool for predicting HNF1B mutations in children and young adults with congenital anomalies of the kidneys and urinary tract.

BACKGROUND: We aimed to develop a tool for predicting HNF1B mutations in children with congenital abnormalities of the kidneys and urinary tract (CAKUT). METHODS: The clinical and laboratory data from 234 children and young adults with known HNF1B mutation status were collected and analyzed retrospectively. All subjects were randomly divided into a training (70%) and a validation set (30%). A random forest model was constructed to predict HNF1B mutations. The recursive feature elimination algorithm was used for feature selection for the model, and receiver operating characteristic curve statistics was used to verify its predictive effect. RESULTS: A total of 213 patients were analyzed, including HNF1B-positive (mut + , n = 109) and HNF1B-negative (mut - , n = 104) subjects. The majority of patients had mild chronic kidney disease. Kidney phenotype was similar between groups, but bilateral kidney anomalies were more frequent in the mut + group. Hypomagnesemia and hypermagnesuria were the most common abnormalities in mut + patients and were highly selective of HNF1B. Hypomagnesemia based on age-appropriate norms had a better discriminatory value than the age-independent cutoff of 0.7 mmol/l. Pancreatic anomalies were almost exclusively found in mut + patients. No subjects had hypokalemia; the mean serum potassium level was lower in the HNF1B cohort. The abovementioned, discriminative parameters were selected for the model, which showed a good performance (area under the curve: 0.85; sensitivity of 93.67%, specificity of 73.57%). A corresponding calculator was developed for use and validation. CONCLUSIONS: This study developed a simple tool for predicting HNF1B mutations in children and young adults with CAKUT.

Depressive disorders in children with chronic kidney disease treated conservatively.

BACKGROUND: Children with chronic kidney disease (CKD) experience a lot of mental and emotional stress, which can lead to the development of depressive disorders. The prevalence of depressive disorders in CKD children is estimated to be between 7% and 35%. OBJECTIVES: The aim of our study was to analyze the prevalence and characteristics of depression and depressive symptoms in children and adolescents with CKD treated conservatively. MATERIAL AND METHODS: The cross-sectional, multicenter study was conducted in 73 CKD children aged 8-18 and in 92 of their parents. To assess the mental wellbeing of CKD children, Kovacs's Children's Depression Inventory 2 (CDI2) was used as CDI2: Self-Report and CDI2: Parent Form. RESULTS: The majority of CKD children acquired medium scores in CDI2, 11% of participants reported symptoms suggesting depressive disorder, and among them 8.2% met the criteria for depression. A significant relationship was found between age and interpersonal problems, age at CKD diagnosis, and total score and ineffectiveness, CKD duration and total score/emotional problems. Depressive symptoms were associated with the stage of CKD, and they differed significantly between stages III and IV. We noticed the child-parent disagreement on reported depressive symptoms. Parents perceive their children's mental state as worse than the children themselves. CONCLUSIONS: There is a problem of depression in children with CKD treated conservatively. Variables associated with depressive symptoms in CKD children treated conservatively require further study. Key factors predisposing to the development of depression seem to be age at the time of diagnosis, disease duration, and progression of CKD from stage III to IV. Disparities between depressive symptoms self-reported by CKD children and their parents' assessment require further analysis. However, these disparaties indicate that the final diagnosis of the occurrence of depressive disorders should be based on a multidimensional assessment of the patient's situation.

Physical Activity and Its Potential Determinants in Obese Children and Adolescents under Specialist Outpatient Care-A Pilot Cross-Sectional Study.

(1) Background: this study aimed to assess the physical activity of obese pediatric patients under specialized outpatient care and its potential determinants. (2) Methods: A total of 83 subjects aged 7-18 years with simple obesity and their parents were enrolled. Data were collected with the use of physical activity questionnaires (PAQs) for children and adolescents and additional questions concerning selected socio-demographic characteristics. (3) Results: The mean final PAQ score was 2.09 ± 0.69. The most frequently chosen types of physical activity included walking, gymnastics, and jogging or running. We found a weak correlation inversely proportional between the child's age and mean final PAQ score (r = -0.25; p = 0.02). Younger children were more active during lunchtime at school and after school compared to adolescents (p = 0.03 and p = 0.04). The final PAQ score differed according to the place of residence; the lowest score was obtained by subjects living in cities >100,000 inhabitants (p = 0.025). We found a positive correlation between PAQ-Ch score and the father's physical activity, and between PAQ-A score and the mother's education. (4) Conclusions: The physical activity of obese pediatric patients is low, particularly in adolescents. It seems that age and place of residence have an impact on the physical activity of obese children and adolescents. The PAQs used in this study are useful in physical activity assessment and identification of time segments during the day in which activity might be improved. However, this requires confirmation in a larger group of pediatric patients.

Antibiotic Prophylaxis in Infants with Grade III, IV, or V Vesicoureteral Reflux.

BACKGROUND: The efficacy of continuous antibiotic prophylaxis in preventing urinary tract infection (UTI) in infants with grade III, IV, or V vesicoureteral reflux is controversial. METHODS: In this investigator-initiated, randomized, open-label trial performed in 39 European centers, we randomly assigned infants 1 to 5 months of age with grade III, IV, or V vesicoureteral reflux and no previous UTIs to receive continuous antibiotic prophylaxis (prophylaxis group) or no treatment (untreated group) for 24 months. The primary outcome was the occurrence of the first UTI during the trial period. Secondary outcomes included new kidney scarring and the estimated glomerular filtration rate (GFR) at 24 months. RESULTS: A total of 292 participants underwent randomization (146 per group). Approximately 75% of the participants were male; the median age was 3 months, and 235 participants (80.5%) had grade IV or V vesicoureteral reflux. In the intention-to-treat analysis, a first UTI occurred in 31 participants (21.2%) in the prophylaxis group and in 52 participants (35.6%) in the untreated group (hazard ratio, 0.55; 95% confidence interval [CI], 0.35 to 0.86; P = 0.008); the number needed to treat for 2 years to prevent one UTI was 7 children (95% CI, 4 to 29). Among untreated participants, 64.4% had no UTI during the trial. The incidence of new kidney scars and the estimated GFR at 24 months did not differ substantially between the two groups. Pseudomonas species, other non-Escherichia coli organisms, and antibiotic resistance were more common in UTI isolates obtained from participants in the prophylaxis group than in isolates obtained from those in the untreated group. Serious adverse events were similar in the two groups. CONCLUSIONS: In infants with grade III, IV, or V vesicoureteral reflux and no previous UTIs, continuous antibiotic prophylaxis provided a small but significant benefit in preventing a first UTI despite an increased occurrence of non-E. coli organisms and antibiotic resistance. (Funded by the Italian Ministry of Health and others; PREDICT ClinicalTrials.gov number, NCT02021006; EudraCT number, 2013-000309-21.).

Assessment of Interleukin-15 (IL-15) Concentration in Children with Idiopathic Nephrotic Syndrome.

Idiopathic nephrotic syndrome (INS) is a chronic glomerular disease in children, characterized by severe proteinuria, hypoalbuminemia, and/or presence of edema and hyperlipidemia. The pathogenesis, however, has not been yet established. The clinical course of the disease is characterized by frequent relapses. Interleukin-15 (IL-15) is a pro-inflammatory cytokine, that apart from its involvement in the immune system, was found to be playing a vital role in various cells' functioning, including renal tissue. It is desirable to look for new predictors of INS. Our study aimed to evaluate IL-15 as a potential marker in the early diagnosis of the disease. The cohort participating in the study consisted of patients hospitalized in Clinical Hospital No. 1 in Zabrze, from December 2019 to December 2021, including study group with INS (n = 30) and control group (n = 44). Results: The concentration of IL-15 in both serum and urine was significantly elevated in patients with INS, compared to healthy controls. The cytokine might serve as a marker of the disease, however, further research on larger study groups is needed.

The Role of Brain-Derived Neurotrophic Factor (BDNF) in Diagnosis and Treatment of Epilepsy, Depression, Schizophrenia, Anorexia Nervosa and Alzheimer's Disease as Highly Drug-Resistant Diseases: A Narrative Review.

Brain-derived neurotrophic factor (BDNF) belongs to the family of neurotrophins, which are growth factors with trophic effects on neurons. BDNF is the most widely distributed neurotrophin in the central nervous system (CNS) and is highly expressed in the prefrontal cortex (PFC) and hippocampus. Its distribution outside the CNS has also been demonstrated, but most studies have focused on its effects in neuropsychiatric disorders. Despite the advances in medicine in recent decades, neurological and psychiatric diseases are still characterized by high drug resistance. This review focuses on the use of BDNF in the developmental assessment, treatment monitoring, and pharmacotherapy of selected diseases, with a particular emphasis on epilepsy, depression, anorexia, obesity, schizophrenia, and Alzheimer's disease. The limitations of using a molecule with such a wide distribution range and inconsistent method of determination are also highlighted.

SARS-CoV-2 Infection as a Possible Trigger for IgA-Associated Vasculitis: A Case Report.

BACKGROUND: IgA-associated vasculitis (IgAV), formerly known as Henoch-Schönlein purpura (HSP) disease, is the most common type of systemic vasculitis observed during developmental age. Available published studies associate the outbreak of the disease with streptococci, adenovirus, parvovirus, mycoplasma, respiratory syncytial virus (RSV), and influenza infection in approximately 50% of patients with HSP, while some emerging reports have described a few cases of COVID-19 infection being associated with HSP in both adults and children. CASE PRESENTATION: a 7-year-old girl was diagnosed with HSP, fulfilling the four required clinical criteria (palpable purpura and abdominal pain, arthralgia and edema, and periodic renal involvement). Infection with SARS-CoV-2 was confirmed via the presence of IgM and IgG antibodies. The disclosure of the Henoch-Schönlein purpura (HSP) disease was preceded by a mild, symptomatically treated infection of the upper respiratory tract. High levels of inflammatory markers were observed during hospitalization, including leukocytosis, an increased neutrophil count and a high neutrophil-to-lymphocyte ratio (NLR). All of these markers are associated with IgAV gastrointestinal bleeding, which was also associated with rotavirus diarrhea observed in the patient. CONCLUSIONS: This case presented by us and similar cases presented by other authors indicate the possible role of SARS-CoV-2 in the development of HSP, but this assumption requires further research and evidence-based verification.

X-linked variations in SHROOM4 are implicated in congenital anomalies of the urinary tract and the anorectal, cardiovascular and central nervous systems.

BACKGROUND: SHROOM4 is thought to play an important role in cytoskeletal modification and development of the early nervous system. Previously, single-nucleotide variants (SNVs) or copy number variations (CNVs) in SHROOM4 have been associated with the neurodevelopmental disorder Stocco dos Santos syndrome, but not with congenital anomalies of the urinary tract and the visceral or the cardiovascular system. METHODS: Here, exome sequencing and CNV analyses besides expression studies in zebrafish and mouse and knockdown (KD) experiments using a splice blocking morpholino in zebrafish were performed to study the role of SHROOM4 during embryonic development. RESULTS: In this study, we identified putative disease-causing SNVs and CNVs in SHROOM4 in six individuals from four families with congenital anomalies of the urinary tract and the anorectal, cardiovascular and central nervous systems (CNS). Embryonic mouse and zebrafish expression studies showed Shroom4 expression in the upper and lower urinary tract, the developing cloaca, the heart and the cerebral CNS. KD studies in zebrafish larvae revealed pronephric cysts, anomalies of the cloaca and the heart, decreased eye-to-head ratio and higher mortality compared with controls. These phenotypes could be rescued by co-injection of human wild-type SHROOM4 mRNA and morpholino. CONCLUSION: The identified SNVs and CNVs in affected individuals with congenital anomalies of the urinary tract, the anorectal, the cardiovascular and the central nervous systems, and subsequent embryonic mouse and zebrafish studies suggest SHROOM4 as a developmental gene for different organ systems.

Outcomes of steroid-resistant nephrotic syndrome in children not treated with intensified immunosuppression.

BACKGROUND: The aim of the current PodoNet registry analysis was to evaluate the outcome of steroid-resistant nephrotic syndrome (SRNS) in children who were not treated with intensified immunosuppression (IIS), focusing on the potential for spontaneous remission and the role of angiotensin blockade on proteinuria reduction. METHODS: Ninety-five pediatric patients who did not receive any IIS were identified in the PodoNet Registry. Competing risk analyses were performed on 67 patients with nephrotic-range proteinuria at disease onset to explore the cumulative rates of complete or partial remission or progression to kidney failure, stratified by underlying etiology (genetic vs. non-genetic SRNS). In addition, Cox proportional hazard analysis was performed to identify factors predicting proteinuria remission. RESULTS: Eighteen of 31 (58.1%) patients with non-genetic SRNS achieved complete remission without IIS, with a cumulative likelihood of 46.2% at 1 year and 57.7% at 2 years. Remission was sustained in 11 children, and only two progressed to kidney failure. In the genetic subgroup (n = 27), complete resolution of proteinuria occurred very rarely and was never sustained; 6 (21.7%) children progressed to kidney failure at 3 years. Almost all children (96.8%) received proteinuria-lowering renin-angiotensin-aldosterone system (RAAS) antagonist treatment. On antiproteinuric treatment, partial remission was achieved in 7 of 31 (22.6%) children with non-genetic SRNS and 9 of 27 children (33.3%) with genetic SRNS. CONCLUSION: Our results demonstrate that spontaneous complete remission can occur in a substantial fraction of children with non-genetic SRNS and milder clinical phenotype. RAAS blockade increases the likelihood of partial remission of proteinuria in all forms of SRNS. A higher resolution version of the Graphical abstract is available as Supplementary information.

Genome-wide association study in patients with posterior urethral valves.

Congenital lower urinary tract obstructions (LUTO) are most often caused by posterior urethral valves (PUV), a male limited anatomical obstruction of the urethra affecting 1 in 4,000 male live births. Little is known about the genetic background of PUV. Here, we report the largest genome-wide association study (GWAS) for PUV in 4 cohorts of patients and controls. The final meta-analysis included 756 patients and 4,823 ethnicity matched controls and comprised 5,754,208 variants that were genotyped or imputed and passed quality control in all 4 cohorts. No genome-wide significant locus was identified, but 33 variants showed suggestive significance (P < 1 × 10-5). When considering only loci with multiple variants residing within < 10 kB of each other showing suggestive significance and with the same effect direction in all 4 cohorts, 3 loci comprising a total of 9 variants remained. These loci resided on chromosomes 13, 16, and 20. The present GWAS and meta-analysis is the largest genetic study on PUV performed to date. The fact that no genome-wide significant locus was identified, can be explained by lack of power or may indicate that common variants do not play a major role in the etiology of PUV. Nevertheless, future studies are warranted to replicate and validate the 3 loci that yielded suggestive associations.

Assessment of Brain-Derived Neurotrophic Factor (BDNF) Concentration in Children with Idiopathic Nephrotic Syndrome.

Idiopathic nephrotic syndrome (INS) is a chronic disease affecting children in early childhood. It is characterized by proteinuria, hypoalbuminemia, edema and hyperlipidemia. To date, the diagnosis is usually established at an advanced stage of proteinuria. Therefore, new methods of early INS detection are desired. This study was designed to assess brain-derived neurotrophic factor (BDNF) as a potential marker in the early diagnosis of INS. The study group included patients with a diagnosis of idiopathic nephrotic syndrome (n = 30) hospitalized in Clinical Hospital No. 1 in Zabrze, from December 2019 to December 2021. Our study shows that serum BDNF concentration decreased and urine BDNF concentration increased in a group of patients with INS, compared with healthy controls. Such outcomes might be related to loss of the BDNF contribution in podocyte structure maintenance. Moreover, we anticipate the role of BDNF in urine protein concentration increase, which could be used as a direct predictor of urine protein fluctuations in clinical practice. Moreover, the ROC curve has also shown that serum BDNF and urine BDNF levels might be useful as an INS marker.

Diagnostic difficulties in the diagnosis of high acute-phase proteins levels in a teenage drug addicted female patient.

BACKGROUND: Youth drug addiction is a significant social and health problem. Symptoms of the disease include a number of neurological, gastrointestinal and cardiovascular disorders. Possible hormonal disorders and dysregulation of the immune system could also occur. CASE PRESENTATION: We describe a case of a teenage patient with multiple diseases such as esophagitis, allergic disease, and numerous behavioral disorders leading to: self-injury of the body, suicide attempts by drugs overdosing, and experimentation with various psychoactive substances (morphine, amphetamine, methamphetamine, codeine). She was also diagnosed with bipolar disorder. A few hours before the admission to the ward, the patient had an intravenous injection of drugs. Toxicological tests confirmed the presence of amphetamine, ecstasy and opioids in the blood and urine. Laboratory tests revealed extremely increased inflammatory parameters, leucopenia, increased levels of IgG, IgA and IgE (total) immunoglobulins, low concentration of vitamin D. Bacteriological examinations were negative. General condition of the patient got better very quickly, antibiotic therapy was abandoned on the 4th day. It was concluded that the cause of the elevated concentration of acute-phase proteins was most likely caused by intoxication with psychoactive drugs. CONCLUSIONS: The discussed case shows the difficulties of differential diagnosis in a teenage patient struggling with many diseases, who has been abusing drugs for several years. Increased inflammatory parameters in the form of an raised PCT, CRP, NLR, PLR values may be caused by many factors. In adolescents who frequently experiment with psychoactive substances, such cause of these disturbances should also be taken into account.

The influence of cord blood renalase and advanced oxidation protein products (AOPPs) on perinatal and anthropometric parameters of newborns of mothers with gestational hypertension.

BACKGROUND: Renalase is an enzyme secreted by the kidneys, which takes part in the regulation of arterial pressure, myocardial contractility and modulation of vascular resistance, but its effect on renalase levels in newborns has not been studied yet. The levels of advanced oxidation protein products (AOPPs) were also evaluated as a marker of oxidative stress. OBJECTIVES: This study examined whether renalase and AOPP levels are different in the cord blood of newborns exposed to gestational hypertension (HT). The association of both factors with perinatal and anthropometric data among the studied patients was assessed. MATERIAL AND METHODS: The study included 89 newborns: 30 newborns from the study group, whose mothers were diagnosed with gestational HT, and 59 newborns born from normal pregnancies, who formed the control group. Anthropometric measurements and perinatal data in newborns in both groups were recorded. RESULTS: A significantly lower (p < 0.001) concentration of renalase was found in the study group (median (Q1-Q3): 23.96 µg/mL (20.63-26.91 µg/mL)) as compared to the control group (median (Q1-Q3): 37.54 µg/mL (33.78-40.02 µg/mL)). In case of AOPPs, a significantly higher (p < 0.001) concentration of AOPPs was observed in the study group (median (Q1-Q3): 131.65 µmol/L (113.80-146.10 µmol/L)) than in the controls (median (Q1-Q3): 93.70 µmol/L (87.10-111.20 µmol/L)). CONCLUSIONS: A significant difference between renalase and AOPP concentrations between the study and control groups has been demonstrated. Both factors may influence anthropometric and perinatal outcomes of newborns.

Effect of Dual-Task Motor-Cognitive Training in Preventing Falls in Vulnerable Elderly Cerebrovascular Patients: A Pilot Study.

Falling is a frequent and major clinical problem among older adults, as well as in patients with chronic cerebrovascular diseases (CVD). At present, sequential (mixed) and simultaneously (dual-task) motor-cognitive trainings are the best approaches to affording patients more autonomy in their everyday motor independence while reducing fall risks and consequences. The objective of this study was to evaluate the efficacy of an advanced and innovative dual-task motor-cognitive rehabilitation program on fall risks in vulnerable older persons with chronic CVD. To this purpose, 26 consecutive older fallers with chronic CVD were recruited, and completed a mixed motor-cognitive or a dual-task motor-cognitive training program. Each patient also underwent two test evaluations to assess balance, gait, fear of falling, and walking performance at pre-and post-intervention. We found that our experimental motor-cognitive dual-task rehabilitation program could be an effective method to improve walking balance, gait, walking speed, and fear of falling, while reducing the risk of falls in older people with chronic CVD. Furthermore, results show that the simultaneous motor-cognitive training is more effective than the sequential motor-cognitive training. Therefore, our study brings innovative data, which can contribute positively to the management of this population.

Parathyroid hormone and phosphate homeostasis in patients with Bartter and Gitelman syndrome: an international cross-sectional study.

BACKGROUND: Small cohort studies have reported high parathyroid hormone (PTH) levels in patients with Bartter syndrome and lower serum phosphate levels have anecdotally been reported in patients with Gitelman syndrome. In this cross-sectional study, we assessed PTH and phosphate homeostasis in a large cohort of patients with salt-losing tubulopathies. METHODS: Clinical and laboratory data of 589 patients with Bartter and Gitelman syndrome were provided by members of the European Rare Kidney Diseases Reference Network (ERKNet) and the European Society for Paediatric Nephrology (ESPN). RESULTS: A total of 285 patients with Bartter syndrome and 304 patients with Gitelman syndrome were included for analysis. Patients with Bartter syndrome type I and II had the highest median PTH level (7.5 pmol/L) and 56% had hyperparathyroidism (PTH >7.0 pmol/L). Serum calcium was slightly lower in Bartter syndrome type I and II patients with hyperparathyroidism (2.42 versus 2.49 mmol/L; P = .038) compared to those with normal PTH levels and correlated inversely with PTH (rs -0.253; P = .009). Serum phosphate and urinary phosphate excretion did not correlate with PTH. Overall, 22% of patients had low serum phosphate levels (phosphate-standard deviation score < -2), with the highest prevalence in patients with Bartter syndrome type III (32%). Serum phosphate correlated with tubular maximum reabsorption of phosphate/glomerular filtration rate (TmP/GFR) (rs 0.699; P < .001), suggesting renal phosphate wasting. CONCLUSIONS: Hyperparathyroidism is frequent in patients with Bartter syndrome type I and II. Low serum phosphate is observed in a significant number of patients with Bartter and Gitelman syndrome and appears associated with renal phosphate wasting.