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.

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.

The Apical Endocytic-Lysosomal Apparatus in CLCN5 Mutations with Phenotypic-Genotypic Correlations in Three Cases.

Dent disease type 1 is characterized by pathogenic CLCN5 gene variants and impaired receptor-mediated endocytosis in proximal tubules. However, mutation-related abnormalities in proximal tubules have not yet been described. Here, we present three patients with CLCN5 alterations and distinct morphological changes of the apical endocytic-lysosomal apparatus. The proximal tubular ultrastructure was investigated in kidney biopsy samples of three boys genotyped for non-nephrotic proteinuria. Controls: seven patients with nephrotic-range glomerular proteinuria. The genotyping findings revealed an already-known missense mutation in one patient and hitherto undescribed frameshift variants in two patients. Low-molecular-weight proteinuria, focal global glomerulosclerosis, proximal tubular changes, and tubular calcium deposits characterized each case. Three subsets of proximal tubular cells were observed: those without any abnormality, those with aplasia of apical endocytic-lysosomal apparatus and shrinkage of cells, and those with hypoplasia of apical endocytic apparatus, accumulation of proteinaceous substance in dysmorphic lysosomes, and dysmorphic mitochondria. The distribution of subsets varied from patient to patient. In one patient with a frameshift variant, an oxidative stress-like injury of proximal tubular cells and podocytes accompanied the above-mentioned alterations. Focal aplasia/hypoplasia of apical endocytic apparatus and subsequent changes in cytoplasmic organelles characterized proximal tubules in the CLCN5 pathogenic variants.

From pollakiuria to Donnai-Barrow syndrome diagnosis in pediatric age.

We report the case of two siblings with incomplete Donnai-Barrow syndrome (DBS) phenotype carrying three LRP2 variants never associated before with DBS phenotype.

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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 5.5 years, ≈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. CONCLUSIONS: 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.

Long-term clinical characteristics and renal prognosis of children with tubulointerstitial nephritis and uveitis syndrome.

BACKGROUND: Tubulointerstitial nephritis and uveitis (TINU) syndrome is a rare disease, especially in children. Owing to the short-term observational period and the small number of patients analyzed in previous reports, the long-term clinical and laboratory characteristics and renal prognosis of children with TINU syndrome remain unclear. METHODS: In this retrospective observational study, we enrolled 29 children with TINU syndrome from February 1990 to February 2019. RESULTS: During the median follow-up duration of 38 months, the kidney function, urinary ß2 microglobulin-creatinine ratio (U-ß2MG/Cr), and uveitis in the patients had significantly improved at 24, 6, and 36 months after diagnosis. Higher U-ß2MG/Cr was associated with longer duration of kidney function normalization. Half of the patients required uveitis treatment for 5 years after the diagnosis. CONCLUSIONS: Patients with severe low-molecular weight proteinuria at diagnosis needed a longer duration to achieve improvements in kidney function. Uveitis has a much longer treatment period than tubulointerstitial nephritis. This study demonstrates the good prognosis of children with TINU syndrome in terms of their long-term clinical and laboratory characteristics.

Clinical manifestation and genetic findings in three boys with low molecular Weight Proteinuria - three case reports for exploring Dent Disease and Fanconi syndrome.

BACKGROUND: Dent disease is an X-linked form of progressive renal disease. This rare disorder was characterized by hypercalciuria, low molecular weight (LMW) proteinuria and proximal tubular dysfunction, caused by pathogenic variants in CLCN5 (Dent disease 1) or OCRL (Dent disease 2) genes. Fanconi syndrome is a consequence of decreased water and solute resorption in the proximal tubule of the kidney. Fanconi syndrome caused by proximal tubular dysfunction such as Dent disease might occur in early stage of the disease. CASE PRESENTATION: Three cases reported in this study were 3-, 10- and 14-year-old boys, and proteinuria was the first impression in all the cases. All the boys presented with LMW proteinuria and elevated urine albumin-to-creatinine ratio (ACR). Case 1 revealed a pathogenic variant in exon 11 of CLCN5 gene [NM_001127899; c.1444delG] and a nonsense mutation at nucleotide 1509 [p.L503*], and he was diagnosed as Dent disease 1. Case 2 carried a deletion of exon 3 and 4 of OCRL1 gene [NM_000276.4; c.120-238delG…A] and a nonsense mutation at nucleotide 171 in exon 5 [p.E57*], and this boy was diagnosed as Dent disease 2. Genetic analysis of Case 3 showed a missense mutation located in exon 2 of HNF4A gene [EF591040.1; c.253C > T; p.R85W] which is responsible for Fanconi syndrome. All of three pathogenic variants were not registered in GenBank. CONCLUSIONS: Urine protein electrophoresis should be performed for patients with proteinuria. When patients have LMW proteinuria and/or hypercalciuria, definite diagnosis and identification of Dent disease and Fanconi syndrome requires further genetic analyses.

Induced pluripotent stem cell-based disease modeling identifies ligand-induced decay of megalin as a cause of Donnai-Barrow syndrome.

Donnai-Barrow syndrome (DBS) is an autosomal-recessive disorder characterized by multiple pathologies including malformation of forebrain and eyes, as well as resorption defects of the kidney proximal tubule. The underlying cause of DBS are mutations in LRP2, encoding the multifunctional endocytic receptor megalin. Here, we identified a unique missense mutation R3192Q of LRP2 in an affected family that may provide novel insights into the molecular causes of receptor dysfunction in the kidney proximal tubule and other tissues affected in DBS. Using patient-derived induced pluripotent stem cell lines we generated neuroepithelial and kidney cell types as models of the disease. Using these cell models, we documented the inability of megalin R3192Q to properly discharge ligand and ligand-induced receptor decay in lysosomes. Thus, mutant receptors are aberrantly targeted to lysosomes for catabolism, essentially depleting megalin in the presence of ligand in this affected family.

Multicenter study of the clinical features and mutation gene spectrum of Chinese children with Dent disease.

Dent disease is a rare X-linked recessive inherited tubular disease. In this multicenter study, the clinical presentation and genetic background of Chinese children with Dent disease are studied to improve the cognition and diagnostic ability of pediatricians. In this prospective cohort, we described the genotype and phenotype of a national cohort composed of 45 pediatric probands with Dent disease belonging to 45 families from 12 different regions of China recruited from 2014 to 2018 by building up the multicenter registration system. The CLCN5 gene from 32 affected families revealed 28 different mutations. The OCRL gene from 13 affected families revealed 13 different mutations. The incidence of low-molecular-weight proteinuria (LMWP) in both Dent disease type 1 populations and Dent disease type 2 populations was 100.0%; however, the incidence of other manifestations was not high, which was similar to previously reported data. Therefore, LMWP is a key clinical feature that should alert clinicians to the possibility of Dent disease. A high amount of LMWP combined with positive gene test results can be used as the diagnostic criteria for this disease. The diagnostic criteria are helpful in reducing the missed diagnosis of this disease and are beneficial for protecting the renal function of these patients through early diagnosis and early intervention.

Prevalence of low molecular weight proteinuria and Dent disease 1 CLCN5 mutations in proteinuric cohorts.

BACKGROUND: Dent disease type 1 (DD1) is a rare X-linked disorder caused mainly by CLCN5 mutations. Patients may present with nephrotic-range proteinuria leading to erroneous diagnosis of focal segmental glomerulosclerosis (FSGS) and unnecessary immunosuppressive treatments. METHODS: The following cohorts were screened for CLCN5 mutations: Chronic Kidney Disease in Children (CKiD; n = 112); Multicenter FSGS-Clinical Trial (FSGS-CT) (n = 96), and Novel Therapies for Resistant FSGS Trial (FONT) (n = 30). Urinary α1-microglobulin (α1M), albumin (A), total protein (TP), and creatinine (Cr) were assessed from CKiD subjects (n = 104); DD1 patients (n = 14); and DD1 carriers (DC; n = 8). TP/Cr, α1M/Cr, α1M/TP, and A/TP from the CKiD cohort were compared with DD1 and DC. RESULTS: No CLCN5 mutations were detected. TP/Cr was lower in DC and CKiD with tubulointerstitial disease than in DD1 and CKiD with glomerular disease (p < 0.002). α1M/Cr was higher in DD1 than in CKiD and DC (p < 0.001). A/TP was lower in DD1, DC, and CKiD with tubulointerstitial disease and higher in CKiD with glomerular disease (p < 0.001). Thresholds for A/TP of ≤ 0.21 and α1M/Cr of ≥ 120 mg/g (> 13.6 mg/mmol) creatinine were good screens for Dent disease. CONCLUSIONS: CLCN5 mutations were not seen in screened CKiD/FSGS cohorts. In our study, a cutoff of TP/Cr > 600 mg/g (> 68 mg/mmol) and A/TP of < 0.3 had a high sensitivity and specificity to distinguish DD1 from both CKiD glomerular and tubulointerstitial cohorts. α1M/Cr ≥ 120 mg/g (> 13.6 mg/mmol) had the highest sensitivity and specificity when differentiating DD1 and studied CKiD populations.

Bone marrow transplantation improves proximal tubule dysfunction in a mouse model of Dent disease.

Dent disease is a rare X-linked tubulopathy caused by mutations in the endosomal chloride-proton exchanger (ClC-5) resulting in defective receptor-mediated endocytosis and severe proximal tubule dysfunction. Bone marrow transplantation has recently been shown to preserve kidney function in cystinosis, a lysosomal storage disease causing proximal tubule dysfunction. Here we test the effects of bone marrow transplantation in Clcn5Y/- mice, a faithful model for Dent disease. Transplantation of wild-type bone marrow in Clcn5Y/- mice significantly improved proximal tubule dysfunction, with decreased low-molecular-weight proteinuria, glycosuria, calciuria, and polyuria four months after transplantation, compared to Clcn5Y/- mice transplanted with ClC-5 knockout bone marrow. Bone marrow-derived cells engrafted in the interstitium, surrounding proximal tubule cells, which showed a rescue of the apical expression of ClC-5 and megalin receptors. The improvement of proximal tubule dysfunction correlated with Clcn5 gene expression in kidneys of mice transplanted with wild-type bone marrow cells. Coculture of Clcn5Y/- proximal tubule cells with bone marrow-derived cells confirmed rescue of ClC-5 and megalin, resulting in improved endocytosis. Nanotubular extensions between the engrafted bone marrow-derived cells and proximal tubule cells were observed in vivo and in vitro. No rescue was found when the formation of the tunneling nanotubes was prevented by actin depolymerization or when cells were physically separated by transwell inserts. Thus, bone marrow transplantation may rescue the epithelial phenotype due to an inherited endosomal defect. Direct contacts between bone marrow-derived cells and diseased tubular cells play a key role in the rescue mechanism.

Proteinuria in Dent disease: a review of the literature.

BACKGROUND: Dent disease is a rare X-linked recessive proximal tubulopathy caused by mutations in CLCN5 (Dent-1) or OCRL (Dent-2). As a rule, total protein excretion (TPE) is low in tubular proteinuria compared with glomerular disease. Several authors have reported nephrotic-range proteinuria (NP) and glomerulosclerosis in Dent disease. Therefore, we aimed to analyze protein excretion in patients with documented CLCN5 or OCRL mutations in a systematic literature review. DESIGN: PubMed and Embase were searched for cases with documented CLCN5 or OCRL mutations and (semi-)quantitative data on protein excretion. The most reliable data (i.e., TPE > protein-creatinine ratio > Albustix) was used for NP classification. RESULTS: Data were available on 148 patients from 47 reports: 126 had a CLCN5 and 22 an OCRLmutation. TPE was not significantly different between both forms (p = 0.11). Fifty-five of 126 (43.7 %) Dent-1 vs 13/22 (59.1 %) Dent-2 patients met the definition of NP (p = 0.25). Serum albumin was normal in all reported cases (24/148). Glomerulosclerosis was noted in 20/32 kidney biopsies and was strongly related to tubulointerstitial fibrosis, but not to kidney function or proteinuria. CONCLUSION: More than half of the patients with both forms of Dent disease have NP, and the presence of low molecular weight proteinuria in a patient with NP in the absence of edema and hypoalbuminemia should prompt genetic testing. Even with normal renal function, glomerulosclerosis and tubulointerstitial fibrosis are present in Dent disease. The role of proteinuria in the course of the disease needs to be examined further in longitudinal studies.

Does Dent disease remain an underrecognized cause for young boys with focal glomerulosclerosis?

Focal glomerulosclerosis (FGS) is a histologic entity that causes significant proteinuria in children. Although its etiology varies, recent reports indicated that some young male patients with FGS had underlying Dent disease. We describe the case of a 14-year-old Japanese boy who presented with persistent non-nephrotic range proteinuria, hematuria, and renal insufficiency. The patient was initially diagnosed as having FGS associated with scattered tubulointerstitial fibrosis. Although he had neither nephrocalcinosis nor family history of renal disease including urolithiasis, increased excretion of urinary ß2 microglobulin was noted. Genetic analysis for Dent disease indicated a mutation (c.726 + 1G > A) in Chloride Channel, Voltage-Sensitive 5 (CLCN5). Given a recent hypothesis that Dent disease may be underrecognized in children with FGS, a careful diagnostic evaluation for possible underlying Dent disease should be considered in young boys who present with persistent albuminuria associated with high-grade low-molecular-weight proteinuria.

Mutation Update of the CLCN5 Gene Responsible for Dent Disease 1.

Dent disease is a rare X-linked tubulopathy characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis and/or nephrolithiasis, progressive renal failure, and variable manifestations of other proximal tubule dysfunctions. It often progresses over a few decades to chronic renal insufficiency, and therefore molecular characterization is important to allow appropriate genetic counseling. Two genetic subtypes have been described to date: Dent disease 1 is caused by mutations of the CLCN5 gene, coding for the chloride/proton exchanger ClC-5; and Dent disease 2 by mutations of the OCRL gene, coding for the inositol polyphosphate 5-phosphatase OCRL-1. Herein, we review previously reported mutations (n = 192) and their associated phenotype in 377 male patients with Dent disease 1 and describe phenotype and novel (n = 42) and recurrent mutations (n = 24) in a large cohort of 117 Dent disease 1 patients belonging to 90 families. The novel missense and in-frame mutations described were mapped onto a three-dimensional homology model of the ClC-5 protein. This analysis suggests that these mutations affect the dimerization process, helix stability, or transport. The phenotype of our cohort patients supports and extends the phenotype that has been reported in smaller studies.

Japanese Dent disease has a wider clinical spectrum than Dent disease in Europe/USA: genetic and clinical studies of 86 unrelated patients with low-molecular-weight proteinuria.

Dent disease is an X-linked disorder characterized by low-molecular-weight (LMW) proteinuria, hypercalciuria, nephrocalcinosis, urolithiasis and renal dysfunction. Dent disease is caused by mutations in at least two genes, i.e. CLCN5 and OCRL1, and its genetic background and phenotypes are common among European countries and the USA. However, only few studies on Dent disease in Japan, which was originally called 'low-molecular-weight proteinuric disease', have been reported thus far. In this study, we analysed genetic background and clinical phenotype and laboratory data of 86 unrelated Japanese Dent disease patients. The results demonstrated that the genetic basis of Japanese Dent disease was nearly identical to those of Dent disease in other countries. Of 86 unrelated Japanese Dent patients, 61 possessed mutations in CLCN5 (Dent-1), of which 27 were novel mutations; 11 showed mutations in OCRL1 (Dent-2), six of which were novel, and the remaining 14 patients showed no mutations in CLCN5 or OCRL1 (Dent-NI). Despite the similarity in genetic background, hypercalciuria was detected in only 51%, rickets in 2% and nephrocalcinosis in 35%. Although the patients were relatively young, six patients (8%) showed apparent renal dysfunction. Japanese Dent disease has a wider clinical spectrum than Dent disease in Europe and the USA.

Identification of a novel mutation in the CLCN5 gene in a Chinese family with Dent-1 disease.

Dent disease comprises a group of X-linked recessive inherited renal tubular disorders, the symptoms of which include low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrocalcinosis, and progressive renal failure. We sought to characterize the clinical manifestations and to identify the mutations associated with this disease in Chinese patients. In total, 155 DNA samples were collected from one affected individual, four of his family members, and 150 healthy donors. All 12 exons and the exon-intron boundaries of the CLCN5 gene were amplified and directly sequenced in this Chinese family. The proband demonstrated osteomalacia, which had resulted in more than 10 fractures, LMWP, and renal failure. A single base 'G' deletion at nucleotide 246 (c. 246delG) was identified in exon 5 of the CLCN5 gene in this patient, resulting in a frame shift mutation (fsX) that changed the Threonine (Thr) residue in position 83 to Proline (Pro). The proband's mother was found to be a carrier of this mutation. The present study suggests that a novel frameshift mutation (c. 246delG) in exon 5 of the CLCN5 gene is responsible for Dent disease in this case. Our findings also expand the known spectrum of CLCN5 mutations.

Dent's disease: An unusual cause of kidney failure.

Dent's disease is an X-linked recessive disease characterized by proximal tubulopathy with low-molecular weight proteinuria, hypercalciuria, nephrolithiasis, nephrocalcinosis, and kidney failure. It is mainly caused by mutations in the CLCN5 or OCRL1 genes, and only ~ 250 families have been identified with these mutations. We present a 31-year-old male referred to a nephrology consultation due to elevated serum creatinine and a history of nephrolithiasis. Complementary evaluation revealed protein/creatinine ratio of 1.9 g/g and albumin/creatinine ratio of 0.5 g/g, hypercalciuria and medullary nephrocalcinosis. These findings raised the suspicion of Dent's disease, which was confirmed by genetic testing. A missense mutation in the CLCN5 gene (c.810C>G, p.(Ser270Arg)), not previously reported in populational databases, was identified. During the evaluation of the patient, it came to our attention that a first-degree male cousin was being followed in our kidney transplantation unit. Given the unknown etiology of his chronic kidney disease, genetic testing was performed, identifying the same mutation. This case highlights the importance of considering the diagnosis of Dent's disease in the setting of a male patient with chronic kidney disease of unknown etiology, low-molecular-weight proteinuria, hypercalciuria, and nephrocalcinosis. Despite progression to end-stage kidney failure in a significant portion of male patients, there are no reports of recurrence after kidney transplantation.

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.