Low Molecular Weight Proteinuria Research Articles

Two cases of Dent disease type 1 with Bartter-like phenotype and literature review

The clinical presentation, treatment, and follow-up of two boys with type 1 Dent disease who exhibited a Bartter-like phenotype were retropectively analysed. The related literature of pediatric patients with type 1 Dent disease who had hypokalemia and metabolic alkalosis was screened through databases such as PubMed, CNKI, and Wanfang until February 1, 2024, and common features among these patients were summarized through literature review. A total of 7 literatures were included, and 9 children were included in the analysis. All patients were male, presenting with significant low molecular weight proteinuria and hypercalciuria. Other prominent characteristic phenotypes included short stature (7/8), hypophosphatemia (8/9), and rickets (6/8). Seven previously reported patients had missense or nonsense mutations, while 2 patients in this study carried possible pathogenic mutations in the CLCN5 gene, c.315+2T>A (p.?) and c.584dupT (p.I196Yfs*6), respectively. Five patients were able to maintain blood potassium levels around 3 mmol/L with oral potassium chloride solution combined with non-steroidal anti-inflammatory drugs (ibuprofen or indomethacin). The follow-up showed that 2 patients developed chronic kidney disease stage 4 and stage 3 at the age of 13 and 21 years, respectively. The phenotypic overlap between Dent disease and Batter syndrome is considerable,with the distinguishing feature being the presence of significant low molecular weight proteinuria. Patients with type 1 Dent disease presenting with the Bartter-like phenotype have a high prevalence of short stature, hypophosphatemia, and rickets. Non-steroidal anti-inflammatory drugs can be used to correct hypokalemia in patients under periodic renal function assessment.

4-Phenylbutyric Acid Treatment Reduces Low-Molecular-Weight Proteinuria in a Clcn5 Knock-in Mouse Model for Dent Disease-1.

Dent disease-1 (DD-1) is a rare X-linked tubular disorder characterized by low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrolithiasis and nephrocalcinosis. This disease is caused by inactivating mutations in the CLCN5 gene which encodes the voltage-gated ClC-5 chloride/proton antiporter. Currently, the treatment of DD-1 is only supportive and focused on delaying the progression of the disease. Here, we generated and characterized a Clcn5 knock-in mouse model that carries a pathogenic CLCN5 variant, c. 1566_1568delTGT; p.Val523del, which has been previously detected in several DD-1 unrelated patients, and presents the main clinical manifestations of DD-1 such as high levels of urinary b2-microglobulin, phosphate and calcium. Mutation p.Val523del causes partial ClC-5 retention in the endoplasmic reticulum. Additionally, we assessed the ability of sodium 4-phenylbutyrate, a small chemical chaperone, to ameliorate DD-1 symptoms in this mouse model. The proposed model would be of significant value in the investigation of the fundamental pathological processes underlying DD-1 and in the development of effective therapeutic strategies for this rare condition.

A novel transgenic mouse model highlights molecular disruptions involved in the pathogenesis of Dent disease 1

Dent disease (DD) is a hereditary renal disorder characterized by low molecular weight (LMW) proteinuria and progressive renal failure. Inactivating mutations of the CLCN5 gene encoding the 2Cl-/H+exchanger ClC-5 have been identified in patients with DD type 1. ClC-5 is essentially expressed in proximal tubules (PT) where it is thought to play a role in maintaining an efficient endocytosis of LMW proteins. However, the exact pathological roles of ClC-5 in progressive dysfunctions observed in DD type 1 are still unclear. To address this issue, we designed a mouse model carrying the most representative type of ClC-5 missense mutations found in DD patients. These mice showed a characteristic DD type 1 phenotype accompanied by altered endo-lysosomal system and autophagy functions. With ageing, KI mice showed increased renal fibrosis, apoptosis and major changes in cell metabolic functions as already suggested in previous DD models. Furthermore, we made the interesting new discovery that the Lipocalin-2-24p3R pathway might be involved in the progression of the disease. These results suggest a crosstalk between the proximal and distal nephron in the pathogenesis mechanisms involved in DD with an initial PT impairment followed by the Lipocalin-2 internalisation and 24p3R overexpression in more distal segments of the nephron. This first animal model of DD carrying a pathogenic mutation of Clcn5 and our findings pave the way aimed at exploring therapeutic strategies to limit the consequences of ClC-5 disruption in patients with DD type 1 developing chronic kidney disease.

Ketogenic Diet and Progression of Kidney Disease in Animal Models of Nephropathic Cystinosis.

Nephropathic cystinosis is a rare inherited lysosomal storage disorder caused by mutations in the CTNS gene that encodes for cystinosin, a lysosomal cystine/H+ symporter. From the standpoint of the kidneys, patients develop early-onset renal Fanconi syndrome and progressive chronic kidney disease. Current therapy with cysteamine delays but does not prevent kidney failure, and has significant side effects that limit adherence and reduce the quality of life of patients. We have tested biochemically and histologically the effects of ketogenic diet on kidney disease of two animal models of nephropathic cystinosis. When Ctns-/- mice were fed with ketogenic diet from 3 to 12 months of age, we observed significant nearly complete prevention of Fanconi syndrome, including low molecular weight proteinuria, glycosuria and polyuria. Compared to wild-type animals, BUN at 12 months was higher in cystinotic mice fed with standard diet (P<0.001), but not with ketogenic diet. At sacrifice, kidneys of knock out mice fed with ketogenic diet appeared macroscopically similar to those of wild type animals, which was reflected microscopically by a significant reduction of interstitial cell infiltration (CD3 and CD68 positive cells, P<0.01), of interstitial fibrosis (Masson and α-SMA staining, P< 0.001), and of apoptosis (cleaved caspase 3 levels; P<0.001), and by indirect evidence of restoration of a normal autophagic flux (SQSTM1/p62 and LC3-II expression, P<0.05). Beneficial effects of ketogenic diet on tubular function were also observed after mice were fed with this ketogenic diet from the age of 6 months to the age of 15 months, after they had developed proximal tubular dysfunction. Although slightly less pronounced, these results were replicated in Ctns-/- rats fed with ketogenic diet from 2 to 8 months of life. These results indicate significant mitigation of the kidney phenotype in cystinotic animals fed with ketogenic diet.

#102 Increased expression of carbonic anhydrase 4 in megalin deficiency

Abstract Background and Aims Megalin is an endocytic receptor located in the apical membrane of proximal tubule (PT) cells. It prevents low molecular-weight proteinuria by reuptake of a variety of proteins from the filtrate. Megalin is required for normal uptake of Cubilin-bound proteins, but it is unknown if the receptor is important for other apical PT proteins. Carbonic anhydrase 4 (CA4) is an enzyme crucial for PT bicarbonate reuptake. Our aim was to investigate the relationship between the expression patterns of these two proteins. Method A mouse model of kidney-specific mosaic megalin-knockout (M-KO). Liquid chromatography-mass spectrometry (LC-MS) on mouse kidney cortex. Immunohistochemistry (IHC), electron microscopy (EM) and Western blotting (WB) of mouse kidney. Biochemical analysis of mouse blood and urine. Results LC-MS revealed a 4.23-fold increase in CA4 abundance in M-KO mice together with smaller but also statistically significant alterations in other acid-base-associated proteins. IHC shows that the increase in CA4 abundance specifically was in the cells lacking megalin, while cells with megalin retained normal abundance. The same pattern was observed in a biopsy from a patient lacking megalin. WB revealed increased shedding of CA4 in urine from M-KO mice and EM showed mislocalization of CA4. Conclusion We show a hitherto unknown relationship where the expression and subcellular localization of CA4 is altered in PT-cells lacking megalin and show that M-KO mice have altered acid-base handling. Comparable blood parameters at baseline are maintained despite differences in urinary excretion and when challenged with acetazolamide the urinary excretion of the groups becomes alike, however blood parameters become different. While the mechanisms and full extend are unknown, this links megalin to the acid-base regulating systems of the PT.

Clinical features and genetic analysis of 15 Chinese children with dent disease

Objective The clinical characteristics, genetic mutation spectrum, treatment strategies and prognoses of 15 children with Dent disease were retrospectively analyzed to improve pediatricians’ awareness of and attention to this disease. Methods We analyzed the clinical and laboratory data of 15 Chinese children with Dent disease who were diagnosed and treated at our hospital between January 2017 and May 2023 and evaluated the expression of the CLCN5 and OCRL1 genes. Results All 15 patients were male and complained of proteinuria, and the incidence of low-molecular-weight proteinuria (LMWP) was 100.0% in both Dent disease 1 (DD1) and Dent disease 2 (DD2) patients. The incidence of hypercalciuria was 58.3% (7/12) and 66.7% (2/3) in DD1 and DD2 patients, respectively. Nephrocalcinosis and nephrolithiasis were found in 16.7% (2/12) and 8.3% (1/12) of DD1 patients, respectively. Renal biopsy revealed focal segmental glomerulosclerosis (FSGS) in 1 patient, minimal change lesion in 5 patients, and small focal acute tubular injury in 1 patient. A total of 11 mutations in the CLCN5 gene were detected, including 3 missense mutations (25.0%, c.1756C > T, c.1166T > G, and c.1618G > A), 5 frameshift mutations (41.7%, c.407delT, c.1702_c.1703insC, c.137delC, c.665_666delGGinsC, and c.2200delG), and 3 nonsense mutations (25.0%, c.776G > A, c.1609C > T, and c.1152G > A). There was no significant difference in age or clinical phenotype among patients with different mutation types (p > 0.05). All three mutations in the OCRL1 gene were missense mutations (c.1477C > T, c.952C > T, and c.198A > G). Conclusion Pediatric Dent disease is often misdiagnosed. Protein electrophoresis and genetic testing can help to provide an early and correct diagnosis.

Atypical phenotypes and novel OCRL variations in southern Chinese patients with Lowe syndrome.

Lowe syndrome is characterized by the presence of congenital cataracts, psychomotor retardation, and dysfunctional proximal renal tubules. This study presents a case of an atypical phenotype, investigates the genetic characteristics of eight children diagnosed with Lowe syndrome in southern China, and performs functional analysis of the novel variants. Whole-exome sequencing was conducted on eight individuals diagnosed with Lowe syndrome from three medical institutions in southern China. Retrospective collection and analysis of clinical and genetic data were performed, and functional analysis was conducted on the five novel variants. In our cohort, the clinical symptoms of the eight Lowe syndrome individuals varied. One patient was diagnosed with Lowe syndrome but did not present with congenital cataracts. Common features among all patients included cognitive impairment, short stature, and low molecular weight proteinuria. Eight variations in the OCRL gene were identified, encompassing three previously reported and five novel variations. Among the novel variations, three nonsense mutations were determined to be pathogenic, and two patients harboring novel missense variations of uncertain significance exhibited severe typical phenotypes. Furthermore, all novel variants were associated with altered protein expression levels and impacted primary cilia formation. This study describes the first case of an atypical Lowe syndrome patient without congenital cataracts in China and performs a functional analysis of novel variants in the OCRL gene, thereby expanding the understanding of the clinical manifestations and genetic diversity associated with Lowe syndrome.

Nlrp2 deletion ameliorates kidney damage in a mouse model of cystinosis.

Cystinosis is a rare autosomal recessive disorder caused by mutations in the CTNS gene that encodes cystinosin, a ubiquitous lysosomal cystine/H+ antiporter. The hallmark of the disease is progressive accumulation of cystine and cystine crystals in virtually all tissues. At the kidney level, human cystinosis is characterized by the development of renal Fanconi syndrome and progressive glomerular and interstitial damage leading to end-stage kidney disease in the second or third decade of life. The exact molecular mechanisms involved in the pathogenesis of renal disease in cystinosis are incompletely elucidated. We have previously shown upregulation of NLRP2 in human cystinotic proximal tubular epithelial cells and its role in promoting inflammatory and profibrotic responses. Herein, we have investigated the role of NLRP2 in vivo using a mouse model of cystinosis in which we have confirmed upregulation of Nlrp2 in the renal parenchyma. Our studies show that double knock out Ctns-/- Nlrp2-/- animals exhibit delayed development of Fanconi syndrome and kidney tissue damage. Specifically, we observed at 4-6 months of age that animals had less glucosuria and calciuria and markedly preserved renal tissue, as assessed by significantly lower levels of inflammatory cell infiltration, tubular atrophy, and interstitial fibrosis. Also, the mRNA expression of some inflammatory mediators (Cxcl1 and Saa1) and the rate of apoptosis were significantly decreased in 4-6-month old kidneys harvested from Ctns-/- Nlrp2-/- mice compared to those obtained from Ctns-/-mice. At 12-14 months of age, renal histological was markedly altered in both genetic models, although double KO animals had lower degree of polyuria and low molecular weight proteinuria and decreased mRNA expression levels of Il6 and Mcp1. Altogether, these data indicate that Nlrp2 is a potential pharmacological target for delaying progression of kidney disease in cystinosis.

Dent disease 1-linked novel CLCN5 mutations result in aberrant location and reduced ion currents

Dent disease is a rare renal tubular disease with X-linked recessive inheritance characterized by low molecular weight proteinuria (LMWP), hypercalciuria, and nephrocalcinosis. Mutations disrupting the 2Cl−/1H+ exchange activity of chloride voltage-gated channel 5 (CLCN5) have been causally linked to the most common form, Dent disease 1 (DD1), although the pathophysiological mechanisms remain unclear. Here, we conducted the whole exome capture sequencing and bioinformatics analysis within our DD1 cohort to identify two novel causal mutations in CLCN5 (c.749 G > A, p. G250D, c.829 A > C, p. T277P). Molecular dynamics simulations of ClC-5 homology model suggested that these mutations potentially may induce structural changes, destabilizing ClC-5. Overexpression of variants in vitro revealed aberrant subcellular localization in the endoplasmic reticulum (ER), significant accumulation of insoluble aggregates, and disrupted ion transport function in voltage clamp recordings. Moreover, human kidney-2 (HK-2) cells overexpressing either G250D or T277P displayed higher cell-substrate adhesion, migration capability but reduced endocytic function, as well as substantially altered transcriptomic profiles with G250D resulting in stronger deleterious effects. These cumulative findings supported pathogenic role of these ClC-5 mutations in DD1 and suggested a cellular mechanism for disrupted renal function in Dent disease patients, as well as a potential target for diagnostic biomarker or therapeutic strategy development.

A missense mutation in Ehd1 associated with defective spermatogenesis and male infertility.

Normal function of the C-terminal Eps15 homology domain-containing protein 1 (EHD1) has previously been associated with endocytic vesicle trafficking, shaping of intracellular membranes, and ciliogenesis. We recently identified an autosomal recessive missense mutation c.1192C>T (p.R398W) of EHD1 in patients who had low molecular weight proteinuria (0.7-2.1g/d) and high-frequency hearing loss. It was already known from Ehd1 knockout mice that inactivation of Ehd1 can lead to male infertility. However, the exact role of the EHD1 protein and its p.R398W mutant during spermatogenesis remained still unclear. Here, we report the testicular phenotype of a knockin mouse model carrying the p.R398W mutation in the EHD1 protein. Male homozygous knockin mice were infertile, whereas the mutation had no effect on female fertility. Testes and epididymes were significantly reduced in size and weight. The testicular epithelium appeared profoundly damaged and had a disorganized architecture. The composition of developing cell types was altered. Malformed acrosomes covered underdeveloped and misshaped sperm heads. In the sperm tail, midpieces were largely missing indicating disturbed assembly of the sperm tail. Defective structures, i.e., nuclei, acrosomes, and sperm tail midpieces, were observed in large vacuoles scattered throughout the epithelium. Interestingly, cilia formation itself did not appear to be affected, as the axoneme and other parts of the sperm tails except the midpieces appeared to be intact. In wildtype mice, EHD1 co-localized with acrosomal granules on round spermatids, suggesting a role of the EHD1 protein during acrosomal development. Wildtype EHD1 also co-localized with the VPS35 component of the retromer complex, whereas the p.R398W mutant did not. The testicular pathologies appeared very early during the first spermatogenic wave in young mice (starting at 14 dpp) and tubular destruction worsened with age. Taken together, EHD1 plays an important and probably multifaceted role in spermatogenesis in mice. Therefore, EHD1 may also be a hitherto underestimated infertility gene in humans.

Cellular senescence in kidney biopsies is associated with tubular dysfunction and predicts CKD progression in childhood cancer patients with karyomegalic interstitial nephropathy.

Karyomegalic interstitial nephropathy (KIN) has been reported as an incidental finding in patients with childhood cancer treated with ifosfamide. It is defined by the presence of tubular epithelial cells (TECs) with enlarged, irregular, and hyperchromatic nuclei. Cellular senescence has been proposed to be involved in kidney fibrosis in hereditary KIN patients. We report that KIN could be diagnosed 7-32 months after childhood cancer diagnosis in 6/6 consecutive patients biopsied for progressive chronic kidney disease (CKD) of unknown cause between 2018 and 2021. The morphometry of nuclear size distribution and markers for DNA damage (γH2AX), cell-cycle arrest (p21+, Ki67-), and nuclear lamina decay (loss of lamin B1), identified karyomegaly and senescence features in TECs. Polyploidy was assessed by chromosome fluorescence in situ hybridization (FISH). In all six patients the number of p21-positive TECs far exceeded the typically small numbers of truly karyomegalic cells, and p21-positive TECs contained less lysozyme, testifying to defective resorption, which explains the consistently observed low-molecular-weight (LMW) proteinuria. In addition, polyploidy of TEC was observed to correlate with loss of lysozyme staining. Importantly, in the five patients with the largest nuclei, the percentage of p21-positive TECs tightly correlated with estimated glomerular filtration rate loss between biopsy and last follow-up (R2 = 0.93, p < 0.01). We conclude that cellular senescence is associated with tubular dysfunction and predicts CKD progression in childhood cancer patients with KIN and appears to be a prevalent cause of otherwise unexplained CKD and LMW proteinuria in children treated with DNA-damaging and cell stress-inducing therapy including ifosfamide. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

A rare tubulopathy: Dent's disease in the background of focal segmental glomerular sclerosis

Dent's disease is a proximal tubulopathy with heterogeneous genetical background. The typical clinical finding is characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis/nephrolithiasis and progressive chronic kidney failure. The underlying cause of the disease is the genetic defect (most commonly CLCN5 mutation) of the receptor-mediated endocytosis in the structure of proximal tubules. The typical fenotype may be composed of extrarenal symptoms. In the event of clinical suspicion, Dent's disease is only verifiable by genetic testing without the necessity of any kidney biopsy. The clinical case can be associated with nephrotic-range proteinuria or kidney failure as an indication of kidney biopsy. The number of articles available at scientific literatures on Dent's disease with the inclusion of renal histology is very slight. According to the pathophysiology of the highlighted Dent's disease and additionally to the expected tubular pathology, global or focal segmental glomerular sclerosis may apply for the majority of cases. Orv Hetil. 2023; 164(20): 788-791.

Tubulointerstitial nephritis and uveitis syndrome and SARS-CoV-2 infection in an adolescent: just a coincidence in time?

BackgroundDespite recent well-established kidney tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), usually presenting as acute kidney injury (AKI), there are few published cases with SARS-CoV-2-related tubulointerstitial nephritis (TIN). We report an adolescent with TIN and delayed association with uveitis (TINU syndrome), where SARS-CoV-2 spike protein was identified in kidney biopsy.Case-diagnosis/treatmentA 12-year-old girl was assessed for a mild elevation of serum creatinine detected during the evaluation of systemic manifestations including asthenia, anorexia, abdominal pain, vomiting, and weight loss. Data of incomplete proximal tubular dysfunction (hypophosphatemia and hypouricemia with inappropriate urinary losses, low molecular weight proteinuria, and glucosuria) were also associated. Symptoms had initiated after a febrile respiratory infection with no known infectious cause. After 8 weeks, the patient tested positive in PCR for SARS-CoV-2 (Omicron variant). A subsequent percutaneous kidney biopsy revealed TIN and immunofluorescence staining with confocal microscopy detected the presence of SARS-CoV-2 protein S within the kidney interstitium. Steroid therapy was started with gradual tapering. Ten months after onset of clinical manifestations, as serum creatinine remained slightly elevated and kidney ultrasound showed mild bilateral parenchymal cortical thinning, a second percutaneous kidney biopsy was performed, without demonstrating acute inflammation or chronic changes, but SARS-CoV-2 protein S within the kidney tissue was again detected. At that moment, simultaneous routine ophthalmological examination revealed an asymptomatic bilateral anterior uveitis.ConclusionsWe present a patient who was found to have SARS-CoV-2 in kidney tissue several weeks following onset of TINU syndrome. Although simultaneous infection by SARS-CoV-2 could not be demonstrated at onset of symptoms, since no other etiological cause was identified, we hypothesize that SARS-CoV-2 might have been involved in triggering the patient’s illness.

The Site and Type of CLCN5 Genetic Variation Impact the Resulting Dent Disease-1 Phenotype

Dent disease is an X-linked recessive disorder associated with low molecular weight proteinuria (LMWP), nephrocalcinosis, kidney stones, and kidney failure in the third to fifth decade of life. It consists of Dent disease 1 (DD1) (60% of patients) because of pathogenic variants in the CLCN5 gene and Dent disease 2 (DD2) with changes in OCRL. Retrospective review of 162 patients from 121 different families with genetically confirmed DD1 (82 different pathogenic variants validated using American College of Medical Genetics [ACMG] guidelines). Clinical and genetic factors were compared using observational statistics. A total of 110 patients had 51 different truncating (nonsense, frameshifting, large deletions, and canonical splicing) variants, whereas 52 patients had 31 different nontruncating (missense, in-frame, noncanonical splicing, and stop-loss) changes. Sixteen newly described pathogenic variants were found in our cohort. Among patients with truncating variants, lifetime stone events positively correlated with chronic kidney disease (CKD) evolution. Patients with truncating changes also experienced stone events earlier in life and manifested a higher albumin excretion rate than the nontruncating group. Nevertheless, neither age of nephrocalcinosis nor CKD progression varied between the truncating versus nontruncating patients. A large majority of nontruncating changes (26/31; 84%) were clustered in the middle exons that encode the voltage ClC domain whereas truncating changes were spread across the protein. Variants associated with kidney failure were restricted to truncating (11/13 cases), plus a single missense variant previously shown to markedly reduce ClC-5 functional activity that was found in the other 2 individuals. DD1 manifestations, including the risk of kidney stones and progression to kidney failure, may relate to the degree of residual ClC-5 function.

Dent disease manifesting as nephrotic syndrome.

Dent disease is an X-linked recessive renal tubular disorder, which is mainly caused by mutations of the CLCN5 gene and OCRL gene. It is characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis or nephrolithiasis, and progressive renal failure. Nephrotic syndrome is a glomerular disorder characterized by massive proteinuria, hypoalbuminemia, edema, and hyperlipidemia. In this study, we report two cases of Dent disease manifesting as nephrotic syndrome. Two patients were initially diagnosed with nephrotic syndrome due to edema, nephrotic range proteinuria, hypoalbuminemia, and hyperlipidemia, and responded to prednisone and tacrolimus therapy. Genetic testing revealed mutations in the OCRL and CLCN5 genes. They were eventually diagnosed with Dent disease. Nephrotic syndrome is a rare and insidious phenotype of Dent disease, and its pathogenesis is not fully understood. Patients with nephrotic syndrome are recommended to routinely undergo urinary protein classification and urinary calcium testing, especially those with frequently recurrent nephrotic syndrome and poor response to steroid and immunosuppressive therapy. To date, there is no effective drug treatment for Dent disease. About 30% to 80% of patients progress to end-stage renal disease at the age of 30-50.

Spectrum of renal dysfunction after curative parathyroidectomy in symptomatic primary hyperparathyroidism

ObjectiveThe long-term renal consequences of curative parathyroidectomy (PTX) in symptomatic primary hyperparathyroidism (sPHPT) are not well characterized. We aimed to assess renal glomerular and tubular functions in an sPHPT cohort at ≥1 year's follow-up. DesignRetrospective-prospective study. MethodssPHPT patients with preoperative eGFR ≥60mL/min/1.73m2 and in remission (normocalcemic) for ≥1 year after PTX underwent clinical and biochemical assessment (calcium profile, renal parameters). Ammonium chloride and bicarbonate loading tests were performed in patients with renal tubular dysfunction (RTD). ResultsForty-eight patients (31 females) with median plasma PTH 1,029 (338–1604) pg/mL and mean eGFR 109.2±26.0mL/min/1.73m2 at diagnosis were evaluated at 5.62±3.66 years after curative PTX. At follow-up, eGFR was <60mL/min/m2 in 5 patients (10.4%). Patients with >10% drop in eGFR (n=31) had significantly higher pre-PTX plasma PTH (1,137 vs. 687pg/mL), and longer time to post-PTX evaluation (6.8 vs. 3.4 years). RTD was seen in 11 patients (22.9%): urinary low molecular weight proteinuria (14.6%), distal renal tubular acidosis (12.5%), hypophosphatemia (8.3%), and hypokalemia (8.3%); RTD was associated with significantly lower post-PTX eGFR (72.7 vs. 95.4mL/min/m2). Five of the 7 RTD patients undergoing loading test had impaired urinary acidification, whereas none had impaired bicarbonate resorption. ConclusionsReduction in eGFR and subclinical RTD were prevalent at long-term follow-up in the present Asian-Indian cohort with cured sPHPT. Further studies are warranted to understand the clinical implications of these various renal abnormalities.

Clinical and genetic characteristics of Dent's disease type 1 in Europe.

Dent's disease type 1 (DD1) is a rare X-linked nephropathy caused by CLCN5 mutations, characterized by proximal tubule dysfunction, including low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis-nephrocalcinosis, progressive chronic kidney disease (CKD) and kidney failure (KF). Current management is symptomatic and does not prevent disease progression. Here we describe the contemporary DD1 picture across Europe to highlight its unmet needs. A physician-based anonymous international e-survey supported by several European nephrology networks/societies was conducted. Questions focused on DD1 clinical features, diagnostic procedure and mutation spectra. A total of 207 DD1 male patients were reported; clinical data were available for 163 with confirmed CLCN5 mutations. Proteinuria was the most common manifestation (49.1%). During follow-up, all patients showed LMWP, 66.4% nephrocalcinosis, 44.4% hypercalciuria and 26.4% nephrolithiasis. After 5.5years, ≈50% of patients presented with renal dysfunction, 20.7% developed CKD stage ≥3 and 11.1% developed KF. At the last visit, hypercalciuria was more frequent in paediatric patients than in adults (73.4% versus 19.0%). Conversely, nephrolithiasis, nephrocalcinosis and renal dysfunction were more prominent in adults. Furthermore, CKD progressed with age. Despite no clear phenotype/genotype correlation, decreased glomerular filtration rate was more frequent in subjects with CLCN5 mutations affecting the pore or CBS domains compared with those with early-stop mutations. Results from this large DD1 cohort confirm previous findings and provide new insights regarding age and genotype impact on CKD progression. Our data strongly support that DD1 should be considered in male patients with CKD, nephrocalcinosis/hypercalciuria and non-nephrotic proteinuria and provide additional support for new research opportunities.

Persistent Aseptic Pyelonephritis After Acute Bacterial Pyelonephritis: Possible Role of Corticosteroids

Persistent Aseptic Pyelonephritis After Acute Bacterial Pyelonephritis: Possible Role of Corticosteroids

Long-Term Tubular Dysfunction in Childhood Cancer Survivors; DCCSS-LATER 2 Renal Study.

Simple SummaryWe studied survivors of childhood cancer who received cancer treatment that might affect the kidneys and compared them to controls from the general population. We investigated if there was a difference in the occurrence of tubular dysfunction. The tubules are the part of the kidney responsible for reabsorption of needed substances to the blood and the removal of wastes. After around 25 years since their cancer diagnosis, we found that in general there were no differences between survivors and controls, but survivors more often had losses of small proteins in the urine. Yet, some survivors of childhood cancer were found to have an increased risk of tubular dysfunction. Namely, survivors treated with the chemotherapeutic agents ifosfamide, cisplatin or carboplatin. Therefore, these patients should be monitored during their follow-up.The aim of this nationwide cross-sectional cohort study was to determine the prevalence of and risk factors for tubular dysfunction in childhood cancer survivors (CCS). In the DCCSS-LATER 2 Renal study, 1024 CCS (≥5 years after diagnosis), aged ≥ 18 years at study, treated between 1963 and 2001 with potentially nephrotoxic therapy (i.e., nephrectomy, abdominal radiotherapy, total body irradiation, cisplatin, carboplatin, ifosfamide, high-dose cyclophosphamide, or hematopoietic stem cell transplantation) participated, and 500 age- and sex-matched participants from Lifelines acted as controls. Tubular electrolyte loss was defined as low serum levels (magnesium < 0.7 mmol/L, phosphate < 0.7 mmol/L and potassium < 3.6 mmol/L) with increased renal excretion or supplementation. A α1-microglobulin:creatinine ratio > 1.7 mg/mmol was considered as low-molecular weight proteinuria (LMWP). Multivariable risk analyses were performed. After median 25.5 years follow-up, overall prevalence of electrolyte losses in CCS (magnesium 5.6%, potassium 4.5%, phosphate 5.5%) was not higher compared to controls. LMWP was more prevalent (CCS 20.1% versus controls 0.4%). LMWP and magnesium loss were associated with glomerular dysfunction. Ifosfamide was associated with potassium loss, phosphate loss (with cumulative dose > 42 g/m2) and LMWP. Cisplatin was associated with magnesium loss and a cumulative dose > 500 mg/m2 with potassium and phosphate loss. Carboplatin cumulative dose > 2800 mg/m2 was associated with potassium loss. In conclusion, long-term tubular dysfunction is infrequent. Yet, ifosfamide, cisplatin and carboplatin are risk factors.

Dent-2 disease with a Bartter-like phenotype caused by the Asp631Glu mutation in the OCRL gene

BackgroundDent disease is an X-linked disorder characterized by low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis and chronic kidney disease (CKD). It is caused by mutations in the chloride voltage-gated channel 5 (CLCN5) gene (Dent disease-1), or in the OCRL gene (Dent disease-2). It is associated with chronic metabolic acidosis; however metabolic alkalosis has rarely been reported.Case presentationWe present a family with Dent-2 disease and a Bartter-like phenotype. The main clinical problems observed in the proband included a) primary phosphaturia leading to osteomalacia and stunted growth; b) elevated serum calcitriol levels, leading to hypercalcemia, hypercalciuria, nephrolithiasis and nephrocalcinosis; c) severe salt wasting causing hypotension, hyperaldosteronism, hypokalemia and metabolic alkalosis; d) partial nephrogenic diabetes insipidus attributed to hypercalcemia, hypokalemia and nephrocalcinosis; e) albuminuria, LMWP.Phosphorous repletion resulted in abrupt cessation of hypercalciuria and significant improvement of hypophosphatemia, physical stamina and bone histology. Years later, he presented progressive CKD with nephrotic range proteinuria attributed to focal segmental glomerulosclerosis (FSGS). Targeted genetic analysis for several phosphaturic diseases was unsuccessful. Whole Exome Sequencing (WES) revealed a c.1893C > A variant (Asp631Glu) in the OCRL gene which was co-segregated with the disease in male family members.ConclusionsWe present the clinical characteristics of the Asp631Glu mutation in the OCRL gene, presenting as Dent-2 disease with Bartter-like features. Phosphorous repletion resulted in significant improvement of all clinical features except for progressive CKD. Angiotensin blockade improved proteinuria and stabilized kidney function for several years.Graphical abstract