Search Results (57)

Hereditary renal tubulopathies are rare monogenic disorders caused by defects in tubular transport mechanisms that impair the handling of electrolytes, water, and acid–base balance along the nephron. While each tubulopathy is individually uncommon, their collective burden is clinically relevant, as these disorders can severely affect quality of life and predispose to nephrolithiasis, dehydration episodes, and progression to chronic kidney disease. Advances in molecular genetics have identified more than 70 genes involved in renal tubular physiology; however, a substantial proportion of these cases remain genetically unresolved, and marked phenotypic heterogeneity complicates diagnosis and management. This narrative review provides an integrated overview of the main transport systems operating in the different tubular segments of the nephron—proximal tubule, thick ascending limb of the loop of Henle, distal convoluted tubule and collecting duct—summarizing the tubulopathies associated with each segment and discussing in greater detail representative inherited disorders that illustrate the clinical consequences of their dysfunction. We highlight current diagnostic challenges and limitations of existing therapeutic strategies and discuss novel diagnostic approaches as well as emerging treatment options. Improved genetic diagnosis, validation of candidate biomarkers, and the development of novel therapeutic strategies will be essential to advance precision medicine and improve outcomes for patients with inherited renal tubulopathies. Full article

Background: The long-term kidney outcomes in paediatric osteosarcoma survivors treated with nephrotoxic chemotherapeutic agents are not well-described. Methods: We conducted a multi-centre retrospective cohort study and recruited paediatric osteosarcoma survivors who survived beyond 5 years from cancer diagnosis over a 20-year period. Chronic kidney disease (CKD) was defined as evidence of kidney impairment, chronic tubulopathy, and proteinuria upon last follow-up. Results: We included 89 patients (57% males) with a mean follow-up period of 14.9 years. A total of 42 subjects (47.2%) developed CKD, 28 of whom had CKD stage 1 with either chronic tubulopathy or proteinuria; 14 patients had CKD stage 2 (eGFR < 90 mL/min/1.73 m²), while two had CKD stage 3 (eGFR < 60 mL/min/1.73 m²). Chronic tubular dysfunction was reported in 34 patients (38%), with hypomagnesemia being the most common manifestation. Proteinuria and hypertension were infrequently observed, in 3% and 8% of cases, respectively. We found that a history of severe AKI and aminoglycoside exposure during the treatment course were significant risk factors for CKD, but the dose-dependent relationships between the development of CKD and cisplatin, ifosfamide, and methotrexate could not be demonstrated. Conclusions: CKD is prevalent among paediatric osteosarcoma survivors. Caution is needed when using multiple nephrotoxic agents at the same time, as this could increase the risk of CKD in the long run. Multi-disciplinary regular surveillance should be performed to identify and manage CKD early, including kidney function, electrolyte, and proteinuria monitoring. Full article

Gitelman syndrome (GS) is a rare, autosomal recessive salt-losing tubulopathy caused by mutations in the SLC12A3 gene. It involves dysfunction of the sodium-chloride cotransporter positioned on the apical membranes of the distal convoluted tubule cells, causing sodium shortage and mimicking the use of thiazide diuretics. Hyperaldosteronism secondary to sodium depletion and hypovolemia causes hypokalaemia and metabolic alkalosis. This is associated with inhibition of the Transient Receptor Potential Cation Channel, Subfamily M, Member 6 –TRPM6 channel, which leads to urinary magnesium leakage and hypomagnesemia, subsequently stopping PTH secretion and resulting in hypocalcemia and hypocalciuria. Gitelman syndrome frequently presents later in life, as the symptoms are usually not very threatening. However, early identification, diagnosis, and urgent intervention are essential to improve patient prognosis and quality of life. Importantly, both hypomagnesemia and hypokalaemia can impair insulin secretion and sensitivity. Furthermore, hyperaldosteronism caused by the secondary activation of the R-A-A system can also lead to these disorders. Glucose metabolism problems have been shown to prevail amongst GS patients and manifest more frequently in comparison to the general population. When it comes to the treatment used to reduce hyperglycemia in GS-related T2DM, we consider which of the available drugs are the best for those patients. The article analyses the association of Gitelman syndrome with diabetes mellitus based on the available medical literature—as there are no clinical trials or meta-analyses available for this group, it is presented as a narrative review. Full article

Advances in kidney organoid technologies have expanded opportunities to model human renal development, disease, and therapeutic response. Yet pluripotent stem cell-derived organoids remain limited by cellular heterogeneity, incomplete tubular maturation and low scalability, restricting their translational relevance. Tubular-specific organoids, derived from adult kidney epithelium, address many of these constraints by providing stable, reproducible cultures enriched for functional proximal and distal tubular cells. Their polarized transport, metabolic activity and patient-specific phenotypes enable high-fidelity modeling of acute and chronic tubular disorders, nephrotoxicity, and inherited tubulopathies—areas where conventional animal and cell-line models often fall short. In this Perspective, we outline recent advances that position tubuloids as a versatile platform for drug screening, toxicity testing and personalized disease modeling. We highlight emerging integration with microfluidics, biomaterials, and gene-editing strategies that promise greater physiological realism and precision therapeutics. We also discuss persistent barriers that impede broader adoption and clinical translation. We propose a roadmap for advancing tubuloid technologies toward precision nephrology and their future incorporation into diagnostic, pharmacological and regenerative pipelines. Full article

As in adults, urolithiasis is a significant health problem in children from an early age, having a very negative impact on health and quality of life and potentially leading to kidney function impairment. The occurrence of deposits in the urinary tract in a child is almost always the result of significant predisposing factors, including metabolic defects involving the kidney or the entire body (often inherited in a Mendelian fashion), urinary tract defects, or urinary tract infections. Among metabolic disturbances, idiopathic hypercalciuria, preceded by hypocitraturia, is the most common one. Any child with nephrolithiasis requires a careful metabolic evaluation, including blood tests, urinalysis, and, in many cases, molecular diagnosis. This narrative review presents the epidemiology, pathophysiology, and diagnostic process in children with nephrolithiasis. Special emphasis is put on pathophysiological pathways leading to metabolic kidney stone disease and metabolic diagnostic steps in children with urolithiasis, as metabolic disturbances are the most common cause of recurrent urolithiasis in Europe and North America. Nephrolithiasis should be treated as a symptom of renal or systemic disorders, and in every child, the cause of these disorders should be sought to prevent recurrence. Full article

Hypophosphatemia is a rare ion disorder in children, but it carries the risk of serious clinical sequelae in tissues and organs with high energy requirements, such as bone tissue. This article discusses the metabolism of phosphate in the body, the clinical manifestations of hypophosphatemia, and the diagnostic tests necessary in patients with this disorder. Extra-renal causes are analyzed, and renal forms of hypophosphatemia are discussed in detail. Renal hypophosphatemia, depending on the mechanism, is divided into PTH-dependent (e.g., primary hyperparathyroidism), FGF23-dependent (e.g., X-linked hypophosphatemia), and intrinsic renal hypophosphatemia (e.g., Fanconi syndrome). The treatment of hypophosphatemia involves compensating for phosphate deficiency, often simultaneously with the supply of an active form of vitamin D. Always seek causal treatment, such as parathyroidectomy in primary hyperparathyroidism. In the FGF-23-dependent forms of X-linked hypophosphatemia and tumor-induced osteomalacia, burosumab has proven to be an effective and safe drug. Conclusions: a child with hypophosphatemia requires a multidisciplinary approach and determination of the mechanism of phosphate deficiency in the body. Full article

Hydrogen sulfide (H₂S) exerts regulatory functions in kidney diseases. However, its protective role against kidney stone formation remains unclear. Here, we demonstrate that hyperoxaluria or oxalate exposure impairs H₂S formation, leading to tubular injury and calcium oxalate (CaOx) crystal deposition in both in vivo and in vitro models. In male rats fed 5% hydroxy-L-proline (HP), time-dependent increases in urinary supersaturation, tubular damage, and renal CaOx deposition were observed compared to controls. These changes were associated with the decreased expression of H₂S-producing enzymes and elevated urinary secretion of osteopontin (OPN) and Tamm–Horsfall protein (THP). Notably, the protein level and activity of specificity protein 1 (Sp1), a transcription factor regulating these enzymes, were markedly decreased in HP-treated kidneys. Chronic supplementation with the H₂S donor GYY4137 (GYY) significantly attenuated HP-induced tubular injury and CaOx deposition by reducing OPN and THP secretion. Consistent with in vivo results, H₂S donors mitigated oxalate-induced tubular cell damage and CaOx formation in MDCK cells. Mechanistically, oxalate activated cyclic AMP/protein kinase A (PKA) signaling, which promoted OPN and THP secretion; these effects were eradicated by the PKA inhibitor H89 or GYY. These findings indicate that hyperoxaluria impairs Sp1 transcriptional activity, resulting in H₂S deficiency and compromised anticrystallization defense in oxalate-induced tubulopathy. Full article

Renal phosphate transporters NaPi-IIa (SLC34A1) and NaPi-IIc (SLC34A3) play a crucial role in phosphate reabsorption in the proximal tubule. Biallelic loss-of-function variants in SLC34A1 and SLC34A3 cause two rare phosphate-wasting tubulopathies: idiopathic infantile hypercalcemia (IIH) and hereditary hypophosphatemic rickets with hypercalciuria, respectively. The phenotypes associated with these diseases are highly variable and sometimes overlap. Here, we report a rare case of a six-month-old girl of consanguineous parents with symptoms related to these diseases, including failure to thrive, nephrocalcinosis, hypercalcemia, hypophosphatemia with low TRP, elevated levels of 1,25-(OH)₂D₃, and suppressed PTH. An exome sequencing analysis was carried out to determine the genetic variants associated with her disease. Bioinformatics tools were used to assess variant pathogenicity. We identify a novel homozygous mutation in the SLC34A1 gene, c.1361C>T; p.(T454M), and a previously described heterozygous SLC34A3 101 bp deletion. Mutation p.(T454M) affects transmembrane domain 5 of the NaPi-IIa protein, which is involved in substrate binding, probably impairing phosphate transport. Our results suggest the diagnosis of IIH type 2 in our patient and highlight the importance of exome analysis in diagnosing these tubulopathies. We suggest that the coexistent heterozygous SLC34A3 deletion could increase the risk of renal calcifications and the severity of other symptoms. Full article

Renal function refers to the combined actions of the glomerulus and tubular system to achieve homeostasis in bodily fluids. While the glomerulus is essential in the first step of urine formation through a coordinated filtration mechanism, the tubular system carries out active mechanisms of secretion and reabsorption of solutes and proteins using specific transporters in the epithelial cells. The assessment of renal function usually focuses on glomerular function, so the tubular function is often underestimated as a fundamental part of daily clinical practice. Therefore, it is essential to properly understand the tubular physiological mechanisms and their clinical association with prevalent human pathologies. This review discusses the primary solutes handled by the kidneys, including glucose, amino acids, sodium, potassium, calcium, phosphate, citrate, magnesium and uric acid. Additionally, it emphasizes the significance of physicochemical characteristics of urine, such as pH and osmolarity. The use of a concise methodology for the comprehensive assessment of urine should be strengthened in the basic training of nephrologists when dealing with problems such as water and electrolyte balance disorders, acid-base disorders, and harmful effects of commonly used drugs such as chemotherapy, antibiotics, or diuretics to avoid isolated replacement of the solute without carrying out comprehensive approaches, which can lead to potentially severe complications. Full article

Gitelman syndrome (GS) is a rare autosomal recessive renal tubulopathy characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria due to mutations in the SLC12A3 gene. This case report presents a 54-year-old African American female with near syncope and palpitations. The patient had a history of intermittent palpitations and generalized anxiety disorder and was previously diagnosed with GS. On presentation, the patient exhibited symptoms of severe hypokalemia and hypomagnesemia, attributed to medication non-adherence. Laboratory tests confirmed critically low potassium and magnesium levels, with elevated urine sodium and chloride. Treatment was initiated with oral and intravenous potassium and magnesium, leading to the normalization of electrolyte levels. This case highlights the challenges of managing GS, particularly in patients facing socioeconomic barriers that impede medication adherence and healthcare access. Personalized patient education, combined with comprehensive healthcare resources, is essential to mitigate complications and improve long-term outcomes in such cases. Full article

Over the past two decades, Mesoamerican endemic nephropathy (MeN) has become a major public health problem in certain regions of Mexico and Central American countries. The etiology of this disease is multifactorial, and important environmental factors have been described, such as chronic heat stress, recurrent episodes of dehydration, infections, and exposure to toxins of chemical and biological origin. Genetic and epigenetic factors have been proposed to play significant roles in MeN. Recent studies have analyzed the role of these factors in MeN. In some cases, these factors appear to be associated with accelerated deterioration of established kidney disease due to preexisting endothelial dysfunction and tubulopathy. In other cases, they appear to be associated with early kidney damage, even before occupational exposure, suggesting that they may play a relevant role in the genesis of the disease. Other factors appear to act as risk reducers for developing MeN in areas with a high prevalence of the disease. Therefore, this disease has a rather complex multifactorial etiology, with possible polygenic contributions, possible epigenetic phenomena, and multiple environmental factors. Full article

Background: Abnormal sodium-dependent hexose reabsorption in the proximal tubule, accompanied by a functional decrease in sodium and water reabsorption under conditions of increased volemia, may be attributed to a dysfunction of primary transporters related to a genetic defect in the Na,K-ATPase gamma subunit. Methods: We examined two sisters, aged 6 and 8 years, who presented with hypercalciuria, glucosuria, fructosuria, galactosuria, and atypical proteinuria. Primary diabetes, galactosemia, and fructosemia were excluded, suggesting a defect in cellular hexose transport in the proximal tubule. We conducted tests on the family members to assess the impact of gradually increasing volemia, using a water-loading test, on tubular H⁺ transport and urinary excretion of calcium, citrate, endothelin-1 (ET-1), and atypical proteins. Whole-exome sequencing was performed in the affected patients to identify the genetic basis of this phenotype. Results: Extended investigations revealed a complex defect in tubular H⁺ transport, calcium and citrate handling, and atypical proteinuria, resulting from water load-driven overproduction of endothelin-1 (ET-1). Genetic analysis identified a heterozygous pathogenic variant, c.80G>A, p.(Arg27His), in the FXYD2 gene, which encodes the gamma subunit of sodium/potassium-transporting ATPase. Conclusions: Our findings provide evidence that a defect in FXYD2 (splice form a) leads to functional impairment of proximal tubular hexose reabsorption. This is the first report on the metabolic consequences of a pathogenic FXYD2 variant affecting the gamma subunit of sodium/potassium-transporting ATPase in humans. The genotype–phenotype correlation in two siblings with a sodium-dependent defect in fructose, galactose, and glucose renal reabsorption allowed us to characterize a disease with a distinct clinical course and biochemical profile, not previously reported in the medical literature or genetic databases. Analysis of this condition was crucial for the early introduction of reno-protective treatment aimed at slowing the progression of nephropathy and for risk assessment in family members, which was essential for genetic counseling. Full article

Background: X-linked hypophosphatemia (XLH) is a rare disorder characterized by elevated levels of fibroblast growth factor 23 (FGF-23), leading to hypophosphatemia and complications in diagnosis due to its clinical heterogeneity. Metabolomic analysis, which examines metabolites as the final products of cellular processes, is a powerful tool for identifying in vivo biochemical changes, serving as biomarkers of pathological abnormalities, and revealing previously uncharted metabolic pathways. Methods: A multicenter cross-sectional case-control study of adult patients diagnosed with XLH was conducted. Serum metabolomic analysis was performed with an Ultra-Performance Liquid Chromatography equipment (UPLC) coupled to a high-resolution mass spectrometer (MS). An analysis of metabolic pathways using MetaboAnalyst version 5.0 and a quantitative enrichment analysis (QEA) was performed. We employed multivariate statistical models, including a principal component analysis (PCA) and an orthogonal partial least squares discriminant analysis (OPLS-DA) regression model. Results: A cohort of 20 XLH patients and 19 control subjects were recruited. A total of 104 metabolites were identified. The differential metabolites identified included glycine, taurine, hypotaurine, phosphoethanolamine, pyruvate, guanidoacetic acid, serine, succinate, 2-aminobutyric acid, glutamine, 2-hydroxyvaleric acid, methionine, ornithine, phosphorylcholine, hypoxanthine, lysine, and N-methylnicotinamide. Enrichment analysis identified disturbances in key metabolic pathways, including phosphatidylethanolamine biosynthesis, sphingolipid metabolism, and phosphatidylcholine biosynthesis. Additionally, pathways related to cysteine metabolism, glycolysis, and pyruvate metabolism. Conclusions: This study identified significant differences in the metabolic profiles of individuals with XLH compared to healthy controls. These findings enhance understanding of potential pathogenic mechanisms and offer a metabolic basis for further in-depth investigations into XLH. Full article

X-linked hypophosphatemia (XLH) is a rare inherited disorder of renal phosphate wasting with a highly variable phenotype caused by loss-of-function variants in the PHEX gene. The diagnosis of individuals with mild phenotypes can be challenging and often delayed. Here, we describe a three-generation family with a very mild clinical presentation of XLH. The diagnosis was unexpectedly found in a 39-year-old woman who was referred for genetic testing due to an unclear childhood diagnosis of a tubulopathy. Genetic testing performed by next-generation sequencing using a kidney disease gene panel identified a novel non-canonical splice site variant in the PHEX gene. Segregation analysis detected that the consultand’s father, who presented with hypophosphatemia and decreased tubular phosphate reabsorption, and the consultand’s son also carried this variant. RNA studies demonstrated that the non-canonical splice site variant partially altered the splicing of the PHEX gene, as both wild-type and aberrant splicing transcripts were detected in the two male members with only one copy of the PHEX gene. In conclusion, this case contributes to the understanding of the relationship between splicing variants and the variable expressivity of XLH disease. The mild phenotype of this family can be explained by the coexistence of PHEX transcripts with aberrant and wild-type splicing. Full article

The process of SARS-CoV-2 infection, responsible for the COVID-19 pandemic, is carried out through different steps, with the interaction between ACE2 and Spike protein (S) being crucial. Besides of that, the acidic environment of endosomes seems to play a relevant role in the virus uptake into cells and its intracellular replication. Patients affected by two rare genetic tubulopathies, Gitelman’s and Bartter’s Syndromes, and a rare genetic metabolic disease, Fabry Disease, have shown intrinsic protection from SARS-CoV-2 infection and COVID-19 on account of specific intrinsic features that interfere with the virus uptake into cells and its intracellular replication, which will be reported and discussed in this paper, providing interesting insights for present and future research. Full article