Search Results (53)

Background/Objectives: X-linked Alport syndrome (XLAS) arises from pathogenic variants in COL4A5. Truncating variants are generally classified as severe, but whether clinically meaningful heterogeneity exists within this group remains unclear. This study aimed to establish a novel Col4a5 knock-in mouse model based on a clinical variant and to determine whether truncating mutation position influences disease severity. Methods: A de novo COL4A5 frameshift variant, c.2440delG, was identified in a patient with severe early-onset XLAS. A Col4a5-G814fs knock-in mouse was generated by CRISPR/Cas9 on the C57BL/6J inbred mouse strain background and compared with the established Col4a5-G5X nonsense model using survival analysis, serial functional measurements, kidney histopathology, transmission electron microscopy, and RNA sequencing. Results: The Col4a5-G814fs knock-in mouse was successfully generated and showed loss of glomerular α5(IV) collagen chain expression. Compared with G5X mice, G814fs mice exhibited shorter survival (median 141 vs. 161.5 days, p = 0.0004), earlier onset of proteinuria, and more severe kidney functional decline. By 16 weeks, G814fs mice also showed more severe glomerular basement membrane abnormalities and more extensive glomerulosclerosis. RNA sequencing revealed a shared inflammatory gene signature in both models, together with selective upregulation of genes related to the PPAR signaling pathway and fatty acid metabolism in G814fs kidneys. Conclusions: This study reports a novel de novo COL4A5 frameshift variant and establishes the first Col4a5-G814fs knock-in mouse model. Direct comparison with the G5X model shows that distinct truncating COL4A5 mutations can be associated with substantially different disease severity, providing a useful platform for future mechanistic and therapeutic studies in XLAS. Full article

Steroid-resistant nephrotic syndrome (SRNS) in childhood frequently reflects monogenic podocytopathies in which immunosuppression is ineffective. Biallelic variants in MYO1E, encoding the class I myosin Myo1E, cause a distinctive form of focal segmental glomerulosclerosis (FSGS) often accompanied by “Alport-like” multilamination of the glomerular basement membrane (GBM). Early recognition has therapeutic and prognostic implications. A previously healthy 4-year-old boy presented with generalized edema and nephrotic-range proteinuria. Glucocorticoids induced no remission; sequential calcineurin inhibition (cyclosporine, then tacrolimus) and a single dose of ofatumumab yielded only transient, partial reductions in proteinuria. A first biopsy elsewhere showed FSGS with nonspecific IgM/C3 trapping; electron microscopy (EM) was not performed. At age 10, repeat biopsy with EM revealed ~30% segmental foot-process effacement, focal GBM thickening (to 1740 nm), irregular lamina densa multilamination, and lamellar duplications without immune-complex deposits—features highly suggestive of hereditary GBM disease. Targeted sequencing identified compound-heterozygous MYO1E variants segregating in trans: a canonical splice-donor change (c.2785+1G>A) and a frameshift (c.3094_3097del; p.Thr1032Profs*73). Each parent was an unaffected heterozygous carrier; the sibling was negative. Supportive therapy with ramipril was continued. At last follow-up (January 2025), renal function was normal (serum creatinine 0.5 mg/dL; creatinine clearance 122 mL/min) with stable sub-nephrotic proteinuria (0.52 g/day; 16 mg/m² per hour) and normotension. This case broadens clinicopathologic recognition of MYO1E-associated nephropathy and highlights the teaching point that Alport-like GBM changes are not pathognomonic for type IV collagen disorders but may signal defects in podocyte cytoskeletal anchoring. Full article

Background: Inherited kidney diseases represent a genetically and clinically heterogeneous group of disorders affecting both pediatric and adult populations. Advances in next-generation sequencing (NGS) have improved diagnostic precision; however, genotype–phenotype correlations and diagnostic yield vary substantially across disease entities. Methods:We retrospectively evaluated 165 patients referred for genetic testing due to suspected inherited kidney disease. Patients were classified into three clinical groups: polycystic kidney disease, Alport syndrome, and other syndromic patients with inherited kidney diseases. Genetic analysis was performed using NGS with Human Phenotype Ontology–based gene filtering and included evaluation of both single-nucleotide variants and copy number variations. Results: Overall diagnostic yield differed markedly between groups. A molecular diagnosis was achieved in 71.4% of Alport patients, 41.0% of PKD patients, and 70.2% of patients in the Other syndromic group. In the Alport group, variants were identified exclusively in COL4A3, COL4A4, and COL4A5, with pathogenicity and gene involvement correlating with disease severity and the presence of extrarenal manifestations. The PKD group showed predominant involvement of PKD1, followed by PKHD1 and PKD2, while a substantial proportion of patients remained genetically negative, reflecting technical and biological complexity. The Other group exhibited pronounced genetic heterogeneity, with variants distributed across multiple genes involved in tubular, glomerular, metabolic, and ciliopathy-related pathways. Computational assessments demonstrated that several variants of uncertain significance (VUS) were located in functionally critical domains and were predicted to disrupt protein stability, intermolecular interactions, or conserved structural motifs, thereby supporting the biological plausibility of their potential pathogenic impact. Conclusions: Phenotype-driven NGS enables effective molecular diagnosis across diverse inherited kidney diseases while revealing disease-specific differences in diagnostic yield and genotype–phenotype correlations. Systematic inclusion of variants of uncertain significance and careful integration of genetic and clinical data are essential for accurate interpretation and long-term patient management. Collectively, this study enhances understanding of inherited kidney diseases and underscores the value of integrating comprehensive genomic and computational approaches into routine nephrogenetic practice. Full article

Globally, chronic kidney disease (CKD) affects over 800 million individuals and is characterized by significant genetic complexity. More than 600 genes are associated with hereditary kidney disease, which may manifest as isolated kidney issues or as part of a syndrome that also includes extrarenal manifestations. The aim of this study was to identify genetic variants in a group of ten patients who presented with clinical signs suggestive of genetic syndromes associated with CKD, or who were asymptomatic but had a positive family history of CKD. Extensive genetic testing (targeted gene panels and whole-exome sequencing—WES) identified a mutation in the PKD1 gene in 3 out of 10 cases. In one patient, a known mutation in the PKD2 gene was identified. Another four patients were diagnosed with Alport syndrome: three of these presented with de novo missense mutations in the COL4A5 gene, and one patient had a mutation in the COL4A3 gene. One patient was diagnosed with MODY5, caused by a known mutation in the HNF1B gene, and one patient was diagnosed with Bartter syndrome type 1, resulting from a known mutation in the SLC12A1 gene. We present genotype–phenotype correlations, highlighting the particularities of each patient within their family context. Our findings emphasize the importance of genotype–phenotype correlations in refining diagnosis, personalizing therapeutic management, and providing essential genetic counseling for at-risk relatives. Full article

Fabry disease (FD) is an X-linked lysosomal disorder caused by GLA mutations, typically associated with glycosphingolipid accumulation and a wide phenotypic spectrum. The p.R112H variant is generally linked to a non-classic predominantly renal phenotype with mild biochemical abnormalities and slow progression. We report the case of a young woman carrying the R112H mutation who exhibited early-onset kidney involvement and unusually rapid progression to end-stage renal disease. Clinical history, serial evaluations, and kidney biopsy findings initially supported a diagnosis of Fabry nephropathy; however, re-evaluation of the native kidney biopsy revealed marked remodeling and multilamellation of the glomerular basement membrane, suggesting Alport-like lesions. Subsequent genetic testing confirmed a heterozygous pathogenic COL4A4 variant (G912R), indicating coexistence of Fabry disease and autosomal dominant Alport syndrome. This dual genetic condition likely accounted for the accelerated decline in kidney function, in contrast with the typically mild phenotype associated with R112H. Our literature review indicates that coexistence of these two inherited nephropathies has not previously been confirmed either histologically or genetically. This case underscores the importance of integrating genetic and ultrastructural assessment in patients with atypical or rapidly progressive renal disease Full article

Τargeted genetic sequencing in a 6-year-old with steroid-resistant nephrotic syndrome and biopsy findings of focal segmental glomerulosclerosis (FSGS) revealed a novel COL4A3 pathogenic variant (p.Arg341His). Combined with electron microscopy findings of glomerular basement membrane abnormality, this led to a diagnosis of type IV collagen-related nephropathy. This case underscores the benefit of early genetic testing in presumed FSGS for prognosis and avoiding unnecessary immunosuppression in pediatric nephrotic syndrome. Full article

Background/Objectives: Alport syndrome (AS) predominantly presents with X-linked inheritance worldwide. However, the epidemiological landscape remains poorly characterized, particularly among ethnic minority groups like the Roma minority in Slovakia. Our study aimed to investigate the inheritance patterns of AS in this region and determine whether a distinct pattern predominates. Methods: Selective genetic screening for pathogenic variants previously occurring in Slovakia was performed. Samples from patients with persistent (familial) hematuria ± hearing loss who had not yet undergone biopsy or genetic testing were analyzed by high-resolution melting analysis. The prevalence of AS per million (pm) population was calculated by adding information on patients with previously confirmed AS. Results: Twenty-five new cases of ARAS, one digenic form, and two cases of XLAS were identified by screening. In total, we collected information on 46 patients with genetically or bioptically confirmed AS in the region of eastern Slovakia, corresponding to a prevalence of 29 pm population. The c.1598G>A (p.Gly533Asp) pathogenic variant of the collagen type IV alpha 4 chain, which follows an autosomal recessive inheritance pattern, was the most prevalent variant that was exclusively confirmed in Roma patients (n = 35), suggesting a founder effect. Within the Roma community, the prevalence of ARAS (the most prevalent inheritance pattern) corresponds to 133 pm of the Roma population, based on midpoint population estimates. Conclusions: Our findings demonstrate a unique genetic profile of AS in the Roma population, characterized by a high prevalence of ARAS, with implications for genetic counseling and screening strategies. Full article

Variants in COL4A3 and COL4A4 cause autosomal dominant and recessive Alport syndrome, yet data on their distribution and clinical expression in different populations remain limited. This study investigated genotype–phenotype correlations and the distribution of COL4A3/COL4A4 variants in a Lithuanian Alport syndrome cohort. A total of 221 individuals from Lithuania were analyzed for COL4A3 and COL4A4 variants using either next-generation sequencing or Sanger sequencing in order to assess variant distribution and associated clinical features. Only individuals with pathogenic, likely pathogenic, or uncertain significance variants were included. Fifty-two individuals (38 index cases) with pathogenic, likely pathogenic, or variants of uncertain significance were identified, as follows: forty-eight were heterozygous, four had autosomal recessive, and four had digenic Alport syndrome. COL4A3 variants were found in 9.5% (21/221) and COL4A4 in 17.6% (39/221). Among the 28 identified variants, 18 were novel. Glycine substitutions (n = 8) were the most frequent and associated with worse kidney outcomes and increased hearing abnormalities. Hematuria was diagnosed significantly earlier than proteinuria (p = 0.05). Most individuals with autosomal dominant Alport syndrome had normal kidney function (eGFR > 90 mL/min/1.73 m²), while those with autosomal recessive Alport syndrome had more severe disease. Kidney failure occurred in 2/4 (50%) autosomal recessive Alport syndrome and 2/48 (4%) autosomal dominant Alport syndrome cases. A significant inverse correlation was found between eGFR and age in proteinuric individuals (r = –0.737; p = 0.013). This study expands knowledge of Alport syndrome in the Lithuanian population and contributes novel variant data to the global Alport syndrome genetic database. Full article

Chronic kidney disease (CKD) significantly affects canine health, but the precise cellular mechanisms of this condition remain elusive. In this study, we used single-cell RNA sequencing (scRNA-seq) to profile renal cellular gene expression in a canine model of X-linked hereditary nephropathy (XLHN). Dogs with this condition exhibit juvenile-onset CKD similar to that seen in human Alport syndrome. Post-mortem renal cortical tissues from an affected male dog and a heterozygous female dog were processed to obtain single-cell suspensions. In total, we recovered up to 13,190 cells and identified 11 cell types, including major kidney cells and immune cells. Differential gene expression analysis comparing the affected male and heterozygous female dogs identified cell-type specific pathways that differed in a subpopulation of proximal tubule cells. These pathways included the integrin signaling pathway and the pathway for inflammation mediated by chemokine and cytokine signaling. Additionally, using machine learning-empowered digital cytometry, we deconvolved bulk mRNA-seq data from a previous canine study, revealing changes in cell type proportions across CKD stages. These results underline the utility of single-cell methodologies and digital cytometry in veterinary nephrology. Full article

Background and Clinical Significance: Kidney transplantation remains the most effective method of renal replacement therapy. Living donor transplantation offers several advantages—reduced cardiovascular risk, better graft survival, and preemptive intervention. However, donor obesity is a growing concern, as it is usually associated with perioperative and long-term complications, which can affect donor eligibility. Bariatric surgery is a standard recommendation for patients with a BMI over 35 kg/m². There are limited data on the use of pharmacological agents for weight reduction in kidney donors. This case presents a successful conservative treatment with GLP-1 receptor agonist in an obese woman wishing to donate a kidney to her son. Case Presentation: We are presenting the case of a 63-year-old woman with grade II obesity who was initially denied being a kidney donor to her son because of her weight. Under these circumstances, she underwent comprehensive lifestyle modification in the cardio-obesitology clinic (caloric restriction, physical activity, and pharmacological treatment with liraglutide). During the 3-month follow-up, she decreased her BMI to 33.4 kg/m², and subsequent examinations confirmed no surgical contraindications to donating a kidney. Despite hematuria, biopsy and genetic testing revealed a benign carrier condition of Alport syndrome, which, without proteinuria or renal impairment, allowed successful kidney donation. Conclusions: This case demonstrates that conservative pharmacological treatment for body weight reduction with GLP-1 receptor agonists may be an alternative to bariatric surgery for selected obese kidney donor candidates. The presented case highlights the importance of a multidisciplinary and personalized approach. Full article

Pathogenic variants in type IV collagen genes (COL4A3, COL4A4, COL4A5) are classically associated with Alport syndrome (AS), a hereditary nephropathy primarily affecting the glomerular basement membrane (GBM). Recent findings, however, suggest a broader phenotypic spectrum that includes renal cyst formation, raising questions about overlapping mechanisms with other cystic kidney diseases. Clinically, renal cysts have been increasingly reported in patients with autosomal dominant and X-linked forms of Alport syndrome, particularly in association with glycine missense variants. The most recent studies focusing on the cystic phenotype in Alport syndrome provide growing support for the idea that variants in type IV collagen genes are associated with an increased likelihood of developing renal cysts, likely through mechanisms involving the structural integrity of renal basement membranes. In this review, we explore evidence from murine models and human studies indicating defects in collagen IV and discuss their contribution to cystogenesis. These observations underscore the need for broader genetic screening strategies and further investigation into the molecular mechanisms underlying this emerging phenotype. Full article

Background/Objectives: Patients suffering from rare diseases are particularly vulnerable to vitamin D deficiency. The role of vitamin D status in rare disease management remains insufficiently investigated and employed in routine clinical practice. Methods: This review analyses current data on vitamin D status in selected rare diseases of organs involved in vitamin D metabolism: skin (epidermolysis bullosa, morphea), liver (autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis), kidney (Alport syndrome, Fabry disease), and cystic fibrosis as a model of a systemic rare disease. Additionally, this review critically examines potential drug–vitamin D interactions in the context of rare disease patient polypharmacy. Results: Evidence suggests that vitamin D deficiency is prevalent in rare disease patient populations, often at once exacerbating and being simultaneously exacerbated by the underlying condition. Vitamin D deficiency correlates with worse clinical outcomes and lower quality of life across the examined diseases. Immunoregulatory properties of vitamin D appear relevant for rare diseases with autoimmune components. Conclusions: An urgent need for developing disease-specific clinical practice guidelines, implementing routine vitamin D monitoring in rare disease patient care, and introducing tailored supplementation under the principles of precision medicine is emphasized. Full article

Background: Alport syndrome (AS) is one of the most common monogenic kidney disorders. Recent studies have highlighted the modifier effect of variants involving podocyte and non-collagenous extracellular matrix (ECM) proteins in AS. Methods: We report a case series of eight patients with genetically proven AS and simultaneous variants involving podocyte and non-collagenous ECM proteins. Our aim is to describe the influence of such variants on the phenotype of patients with AS. Results: We identified 10 different type IV collagen variants. Patients were diagnosed with autosomal dominant (3/8), autosomal recessive (2/8), digenic (2/8) and X-linked AS (1/8). There were eight different variants involving podocyte and non-collagenous ECM proteins. The genes involved were CRB2, LAMA5, LAMB2, NUP107, MYO1E and PLCE1. Four patients (LAMB2, LAMA5 and PLCE1 variants) presented with nephrotic syndrome or nephrotic range proteinuria. Two patients had hearing loss. Most patients (7/8) had a family history of kidney disease. Two patients (LAMB2 and LAMA5 variants) were diagnosed with focal segmental glomerulosclerosis. Two patients developed end-stage kidney disease (LAMA5, MYO1E and NUP107 variants). Conclusions: Although mutations of podocyte and ECM proteins do not have phenotypic expression in monoallelic form, the presence of such variants could explain the phenotypic variability of AS. Full article

Background: Alport syndrome (AS) is a clinically and genetically heterogeneous glomerulopathy resulting from pathogenic variants in COL4A3, COL4A4, and COL4A5. Genetic diagnosis is increasingly being conducted using next-generation sequencing (NGS). Methods: Within eight years, we examined a group of 247 Polish individuals and found in total 138 unrelated probands suspected with AS based on clinical course, laboratory findings, and/or family history, as well as the total of 109 family members. We applied a targeted NGS panel to identify the genetic spectrum of AS. Known and novel variants were revealed, and detailed evaluation was performed according to ACMG/AMP guidelines to classify them as pathogenic/likely pathogenic/VUS changes. Identified genotypes were compared with clinical manifestations: hematuria, proteinuria, chronic kidney disease, sensorineural hearing impairment, ocular abnormalities, and hypertension. Results: The molecular background was established in 109/138 probands. Overall, 79 different COL4A3-COL4A5 changes (56 known and 23 novel) were revealed. About 97% were SNVs, and only two COL4A5 CNVs were identified. In total, 11 recurrent COL4A3-COL4A5 variants were observed, including the most frequent COL4A5:p.Gly624Asp, accounting for 31% of X-linked AS. Conclusions: The use of NGS panel has shown considerable promise in the field of AS, increasing diagnostic rate to 79% and reducing time to diagnosis. The phenotype-driven gene panel, specific for genetic diseases in the pediatric population, is an affordable alternative to WGS and WES, offering comparable diagnostic efficacy and supporting its implementation as a first-line genetic test in rare diseases, including AS. Based on the obtained genotype–phenotype correlation, we assessed that NGS allows us to avoid invasive renal biopsy in AS diagnosis. It provides AS confirmation/exclusion, atypical AS identification, symptomatic/asymptomatic monoallelic COL4A3-COL4A5 carrier (especially COL4A5 females) determination, and inheritance pattern establishment. AS diagnosis confirmation enables clinical course prediction and is crucial for the early introduction of renoprotective treatment with renin–angiotensin–aldosterone system blockade, aimed at slowing the disease progression and estimating the risk in family members, which is important for genetic counselling. Full article

Mitochondrial dysfunction is a critical factor in the pathogenesis of Alport syndrome (AS), contributing to podocyte injury and disease progression. Ezetimibe, a lipid-lowering drug, is known to inhibit cholesterol and fatty acid uptake and to reduce triglyceride content in the kidney cortex of mice with AS. However, its effects on lipid droplet (LD) utilization by mitochondria have not been explored. Transmission electron microscopy (TEM) and mitochondrial functional assays (ATP production, mitochondrial membrane potential, and citrate synthase activity) were used to investigate the impact of ezetimibe on LD–mitochondria contact formation and mitochondrial function in Col4a3KO (AS) and wildtype (WT) podocytes. TEM analysis revealed significant mitochondrial abnormalities in AS podocytes, including swollen mitochondria and reduced cristae density, while mitochondrial function assays showed decreased ATP production and lowered mitochondrial membrane potential. AS podocytes also demonstrated a higher content of LD but with reduced LD–mitochondria contact sites. Ezetimibe treatment significantly increased the number of LD–mitochondria contact sites, enhanced fatty acid transfer efficiency, and reduced intracellular lipid accumulation. These changes were associated with a marked reduction in the markers of lipotoxicity, such as apoptosis and oxidative stress. Mitochondrial function was significantly improved, evidenced by increased basal respiration, ATP production, maximal respiration capacity, and the restoration of mitochondrial membrane potential. Additionally, mitochondrial swelling was significantly reduced in ezetimibe-treated AS podocytes. Our findings reveal a novel role for ezetimibe in enhancing LD–mitochondria contact formation, leading to more efficient fatty acid transfer, reduced lipotoxicity, and improved mitochondrial function in AS podocytes. These results suggest that ezetimibe could be a promising therapeutic agent for treating mitochondrial dysfunction and lipid metabolism abnormalities in AS. Full article