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Gibson JT, Sadeghi-Alavijeh O, Gale DP, Rothe H, Savige J. Pathogenicity of missense variants affecting the collagen IV α5 carboxy non-collagenous domain in X-linked Alport syndrome. Sci Rep 2022; 12:11257. [PMID: 35789182 PMCID: PMC9253329 DOI: 10.1038/s41598-022-14928-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 06/15/2022] [Indexed: 12/05/2022] Open
Abstract
X-linked Alport syndrome is a genetic kidney disease caused by pathogenic COL4A5 variants, but little is known of the consequences of missense variants affecting the NC1 domain of the corresponding collagen IV α5 chain. This study examined these variants in a normal (gnomAD) and other databases (LOVD, Clin Var and 100,000 Genomes Project) to determine their pathogenicity and clinical significance. Males with Cys substitutions in the collagen IV α5 NC1 domain reported in LOVD (n = 25) were examined for typical Alport features, including age at kidney failure. All NC1 variants in LOVD (n = 86) were then assessed for structural damage using an online computational tool, Missense3D. Variants in the ClinVar, gnomAD and 100,000 Genomes Project databases were also examined for structural effects. Predicted damage associated with NC1 substitutions was then correlated with the level of conservation of the affected residues. Cys substitutions in males were associated with the typical features of X-linked Alport syndrome, with a median age at kidney failure of 31 years. NC1 substitutions predicted to cause structural damage were overrepresented in LOVD (p < 0.001), and those affecting Cys residues or 'buried' Gly residues were more common than expected (both p < 0.001). Most NC1 substitutions in gnomAD (88%) were predicted to be structurally-neutral. Substitutions affecting conserved residues resulted in more structural damage than those affecting non-conserved residues (p < 0.001). Many pathogenic missense variants affecting the collagen IV α5 NC1 domain have their effect through molecular structural damage and 3D modelling is a useful tool in their assessment.
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Affiliation(s)
- Joel T Gibson
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Parkville, VIC, 3050, Australia
| | - Omid Sadeghi-Alavijeh
- Department of Renal Medicine, University College London, London, UK
- Genomics England, Queen Mary University of London, London, UK
| | - Daniel P Gale
- Department of Renal Medicine, University College London, London, UK
- Genomics England, Queen Mary University of London, London, UK
| | - Hansjörg Rothe
- Centre for Nephrology and Metabolic Disorders, 02943, Weisswasser, Germany
| | - Judy Savige
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Parkville, VIC, 3050, Australia.
- Genomics England, Queen Mary University of London, London, UK.
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Aoto Y, Horinouchi T, Yamamura T, Kondo A, Nagai S, Ishiko S, Okada E, Rossanti R, Sakakibara N, Nagano C, Awano H, Nagase H, Shima Y, Nakanishi K, Matsuo M, Iijima K, Nozu K. Last Nucleotide Substitutions of COL4A5 Exons Cause Aberrant Splicing. Kidney Int Rep 2022; 7:108-116. [PMID: 35005319 PMCID: PMC8720670 DOI: 10.1016/j.ekir.2021.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/08/2021] [Accepted: 10/11/2021] [Indexed: 12/23/2022] Open
Abstract
Introduction COL4A5 is a causative gene of X-linked Alport syndrome (XLAS). Male patients with XLAS with nonsense variants have the most severe phenotypes of early onset end-stage kidney disease (ESKD); those with splicing variants have middle phenotypes and those with missense variants have the mildest phenotypes. Therefore, genotyping for male patients with XLAS can be used to predict kidney prognosis. Single-base substitutions at the last nucleotide position in each exon are known to affect splicing patterns and could be splicing variants. Nevertheless, in XLAS, these variants are generally considered to be missense variants, without conducting a transcript analysis, which underestimates some patients as having mild phenotypes. This study aimed to investigate whether single-base substitutions at the last nucleotide position of COL4A5 exons cause aberrant splicing. Methods In total, 20 variants were found in the Human Gene Mutation Database (n = 14) and our cohort (n = 6). We performed functional splicing assays using a hybrid minigene analysis and in vivo transcript analyses of patients’ samples when available. Then, we investigated genotype–phenotype correlations for patients with splicing variants detected in this study by comparing data from our previous studies. Results Among the 20 variants, 17 (85%) caused aberrant splicing. Male patients with splicing variants had more severe phenotypes when compared with those with missense variants. Findings from the in vivo analyses for 3 variants were identical to those from the minigene assay. Conclusion Our study revealed that most single-base substitutions at the last nucleotide position of COL4A5 exons result in splicing variants, rather than missense variants, thereby leading to more severe phenotypes.
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Affiliation(s)
- Yuya Aoto
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tomoko Horinouchi
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tomohiko Yamamura
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Atsushi Kondo
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Sadayuki Nagai
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shinya Ishiko
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Eri Okada
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Rini Rossanti
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Nana Sakakibara
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - China Nagano
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroyuki Awano
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Nagase
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yuko Shima
- Department of Pediatrics, Wakayama Medical University, Wakayama, Japan
| | - Koichi Nakanishi
- Department of Child Health and Welfare (Pediatrics), Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan
| | - Masafumi Matsuo
- Department of Physical Therapy, Faculty of Rehabilitation, Kobe Gakuin University, Kobe, Japan
| | - Kazumoto Iijima
- Hyogo Prefectural Kobe Children's Hospital, Hyogo, Japan.,Department of Advanced Pediatric Medicine, Kobe University Graduate School of Medicine, Hyogo, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
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Mastrangelo A, Giani M, Groppali E, Castorina P, Soldà G, Robusto M, Fallerini C, Bruttini M, Renieri A, Montini G. X-Linked Alport Syndrome in Women: Genotype and Clinical Course in 24 Cases. Front Med (Lausanne) 2020; 7:580376. [PMID: 33330536 PMCID: PMC7719790 DOI: 10.3389/fmed.2020.580376] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/19/2020] [Indexed: 11/30/2022] Open
Abstract
Objectives: X-linked Alport syndrome (XLAS) females are at risk of developing proteinuria and chronic kidney damage (CKD). The aim of this study is to evaluate the genotype-phenotype correlation in this rare population. Materials and Methods: This is a prospective, observational study of XLAS females, confirmed by a pathogenic mutation in COL4A5 and renal ultrastructural evaluation. Proteinuria, renal function and extrarenal involvement were monitored during follow-up. Patients were divided in 2 groups, according to mutations in COL4A5: missense (Group 1) and non-missense variants (Group 2). Results: Twenty-four XLAS females, aged 10.6 ± 10.4 years at clinical onset (mean follow-up: 13.1 ± 12.6 years) were recruited between 2000 and 2017 at a single center. In group 1 there were 10 patients and in group 2, 14 (mean age at the end of follow-up: 24.9 ± 13.6 and 23.2 ± 13.8 years, respectively). One patient in Group 1 and 9 in Group 2 (p = 0.013) developed proteinuria during follow-up. Mean eGFR at last follow-up was lower in Group 2 (p = 0.027), where two patients developed CKD. No differences in hearing loss were documented among the two groups. Two patients in Group 2 carried one mutation in both COL4A5 and COL4A3 (digenic inheritance) and were proteinuric. In one family, the mother presented only hematuria while the daughter was proteinuric and presented a greater inactivation of the X chromosome carrying the wild-type allele. Conclusions: The appearance of proteinuria and CKD is more frequent in patients with severe variants. Carrying digenic inheritance and skewed XCI seem to be additional risk factors for proteinuria in XLAS females.
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Affiliation(s)
- Antonio Mastrangelo
- Pediatric Nephrology, Dialysis and Transplant Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Marisa Giani
- Pediatric Nephrology, Dialysis and Transplant Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Elena Groppali
- Department of Pediatrics, V. Buzzi Children's Hospital, Milan, Italy
| | | | - Giulia Soldà
- Dipartimento di Scienze Biomediche, Humanitas University, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy
| | - Michela Robusto
- Experimental Therapeutics Program, Istituto FIRC di Oncologia Molecolare-Fondazione Italiana per la Ricerca sul Cancro Institute of Molecular Oncology Foundation, Milan, Italy
| | | | - Mirella Bruttini
- Azienda Ospedaliera Universitaria Senese, Medical Genetics, University of Siena, Siena, Italy
| | - Alessandra Renieri
- Azienda Ospedaliera Universitaria Senese, Medical Genetics, University of Siena, Siena, Italy
| | - Giovanni Montini
- Pediatric Nephrology, Dialysis and Transplant Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Giuliana and Bernardo Caprotti Chair of Pediatrics, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
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Trimerization and Genotype-Phenotype Correlation of COL4A5 Mutants in Alport Syndrome. Kidney Int Rep 2020; 5:718-726. [PMID: 32405592 PMCID: PMC7210609 DOI: 10.1016/j.ekir.2020.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 01/13/2020] [Accepted: 01/20/2020] [Indexed: 01/08/2023] Open
Abstract
Introduction Alport syndrome is a hereditary glomerulonephritis that results from the disruption of collagen α345(IV) heterotrimerization caused by mutation in COL4A3, COL4A4 or COL4A5 genes. Many clinical studies have elucidated the correlation between genotype and phenotype, but there is still much ambiguity and insufficiency. Here, we focused on the α345(IV) heterotrimerization of α5(IV) missense mutant as a novel factor to further understand the pathophysiology of Alport syndrome. Methods We selected 9 α5(IV) missense mutants with typical glycine substitutions that clinically differed in disease progression. To quantify the trimerization of each mutant, split nanoluciferase-fused α3/α5 mutants and α4 were transfected into the cells, and intracellular and secreted heterotrimer were detected by luminescence using an assay that we developed previously. Results Trimer formation and secretion patterns tended to be similar to the wild type in most of the mutations that did not show proteinuria at a young age. On the other hand, trimer secretion was significantly reduced in all the mutations that showed proteinuria and early onset of renal failure. One of these mutants has low ability of intracellular trimer formation, and the others had the defect of low-level secretion. In addition, the mutant that is assumed to be nonpathogenic has similar trimer formation and secretion pattern as wild-type α5(IV). Conclusion The result of cell-based α345(IV) heterotrimer formation assay was largely correlated with clinical genotype–phenotype. These trimerization assessments provide additional phenotypic considerations and may help to distinguish between pathogenic and nonpathogenic mutations.
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Lin F, Bian F, Zou J, Wu X, Shan J, Lu W, Yao Y, Jiang G, Gale DP. Whole exome sequencing reveals novel COL4A3 and COL4A4 mutations and resolves diagnosis in Chinese families with kidney disease. BMC Nephrol 2014; 15:175. [PMID: 25381091 PMCID: PMC4233041 DOI: 10.1186/1471-2369-15-175] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/28/2014] [Indexed: 01/01/2023] Open
Abstract
Background Collagen IV-related nephropathies, including thin basement membrane nephropathy and Alport Syndrome (AS), are caused by defects in the genes COL4A3, COL4A4 and COL4A5. Diagnosis of these conditions can be hindered by variable penetrance and the presence of non-specific clinical or pathological features. Methods Three families with unexplained inherited kidney disease were recruited from Shanghai, China. Whole exome sequencing (WES) was performed in the index case from each family and co-segregation of candidate pathogenic mutations was tested by Sanger sequencing. Results We identified COL4A4 missense variants [c.G2636A (p.Gly879Glu) and c.C4715T (p.Pro1572Leu)] in the 21-year-old male proband from family 1, who had been diagnosed with mesangial proliferative nephropathy at age 14. COL4A4 c.G2636A, a novel variant, co-segregated with renal disease among maternal relatives. COL4A4 c.C4715T has previously been associated with autosomal recessive AS and was inherited from his clinically unaffected father. In family 2, a novel COL4A3 missense mutation c.G2290A (p.Gly997Glu) was identified in a 45-year-old male diagnosed with focal segmental glomerulosclerosis and was present in all his affected family members, who exhibited disease ranging from isolated microscopic hematuria to end stage renal disease (ESRD). In family 3, ESRD occurred in both male and females who were found to harbor a known AS-causing COL4A5 donor splice site mutation (c.687 + 1G > A). None of these variants were detected among 100 healthy Chinese individuals. Conclusion WES identified 2 novel and 2 known pathogenic COL4A3/COL4A4/COL4A5 mutations in 3 families with previously unexplained inherited kidney disease. These findings highlight the clinical range of collagen IV-related nephropathies and resolved diagnostic confusion arising from atypical or incomplete clinical/histological findings, allowing appropriate counselling and treatment advice to be given. Electronic supplementary material The online version of this article (doi:10.1186/1471-2369-15-175) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | - Gengru Jiang
- Department of Nephrology, Xin Hua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
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Affiliation(s)
- Helen Liapis
- Department of Pathology and Immunology, and Renal Division, Department of Internal Medicine, Washington University School of Medicine, Saint Louis, Missouri
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Deltas C, Pierides A, Voskarides K. Molecular genetics of familial hematuric diseases. Nephrol Dial Transplant 2013; 28:2946-60. [PMID: 24046192 DOI: 10.1093/ndt/gft253] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The familial hematuric diseases are a genetically heterogeneous group of monogenic conditions, caused by mutations in one of several genes. The major genes involved are the following: (i) the collagen IV genes COL4A3/A4/A5 that are expressed in the glomerular basement membranes (GBM) and are responsible for the most frequent forms of microscopic hematuria, namely Alport syndrome (X-linked or autosomal recessive) and thin basement membrane nephropathy (TBMN). (ii) The FN1 gene, expressed in the glomerulus and responsible for a rare form of glomerulopathy with fibronectin deposits (GFND). (iii) CFHR5 gene, a recently recognized regulator of the complement alternative pathway and mutated in a recently revisited form of inherited C3 glomerulonephritis (C3GN), characterized by isolated C3 deposits in the absence of immune complexes. A hallmark feature of all conditions is the age-dependent penetrance and a broad phenotypic heterogeneity in the sense that subsets of patients progress to added proteinuria or proteinuria and chronic renal failure that may or may not lead to end-stage kidney disease (ESKD) anywhere between the second and seventh decade of life. In addition to other excellent laboratory tools that assist the clinician in reaching the correct diagnosis, the molecular analysis emerges as the gold standard in establishing the diagnosis in many cases of doubt due to equivocal findings that complicate the differential diagnosis. Recent work led to the description of candidate genetic modifiers which confer a variable risk for progressing to chronic renal failure when co-inherited on the background of a primary glomerulopathy. Finally, more families are still waiting to be studied and more genes to be mapped and cloned that are responsible for other forms of heritable hematuric diseases. The study of such genes and their protein products will likely shed more light on the structure and function of the glomerular filtration barrier and other important glomerular components.
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Affiliation(s)
- Constantinos Deltas
- Molecular Medicine Research Center and Laboratory of Molecular and Medical Genetics, Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
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Ahmed F, Kamae KK, Jones DJ, Deangelis MM, Hageman GS, Gregory MC, Bernstein PS. Temporal macular thinning associated with X-linked Alport syndrome. JAMA Ophthalmol 2013; 131:777-82. [PMID: 23572034 DOI: 10.1001/jamaophthalmol.2013.1452] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
IMPORTANCE Optical coherence tomography (OCT) findings of temporal macular thinning are important in the diagnosis and prognosis of X-linked Alport syndrome (XLAS). OBJECTIVES To report OCT findings and severity of temporal macular thinning in a cohort with XLAS and to correlate these and other ocular findings with mutation genotype. DESIGN Patients with XLAS underwent genotyping for COL4A5 mutations and complete eye examinations with retinal imaging using spectral domain OCT and fundus photography. Temporal macular thinning was calculated from OCT measurements by comparing the ratio of the retinal thickness of the temporal to the nasal subfields with a published normative database. SETTING University departments of ophthalmology and nephrology. PARTICIPANTS Thirty-two patients from 24 families. MAIN OUTCOME AND MEASURES Temporal thinning index calculated from spectral domain OCT scans. RESULTS All study patients had a mutation associated with the X-linked COL4A5 gene. Eleven different mutations were identified. Eleven of 32 patients (34%) expressed the L1649R mutation. Of a total of 63 eyes with available OCT scans, 44 (70%) had severe pathological temporal macular thinning. The L1649R mutation was associated with the least amount of severe temporal macular thinning and later onset of renal failure. CONCLUSIONS AND RELEVANCE Temporal macular thinning is a prominent sign associated with XLAS, suggesting that OCT measurements are essential in the diagnosis and prognosis of the disease. The L1649R mutation in the COL4A5 gene causes a relatively mild form of XLAS characterized by late-onset renal failure and less frequent, severe temporal macular thinning relative to other COL4A5 mutations. The pathological basis for the retinal abnormalities of XLAS remains to be established.
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Affiliation(s)
- Faisal Ahmed
- Department of Ophthalmology and Visual Sciences, John A Moran Eye Center, University of Utah, University of Utah Health Sciences Center Salt Lake City, UT 84132, USA
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Pierides A, Voskarides K, Kkolou M, Hadjigavriel M, Deltas C. X-linked, COL4A5 hypomorphic Alport mutations such as G624D and P628L may only exhibit thin basement membrane nephropathy with microhematuria and late onset kidney failure. Hippokratia 2013; 17:207-213. [PMID: 24470729 PMCID: PMC3872455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Alport syndrome (ATS) results from X-linked, COL4A5 mutations (85%) or from autosomal recessive homozygous or compound heterozygous COL4A3/A4 mutations (15%), associated with alternate thinning and thickening as well as splitting and lamellation of the glomerular basement membranes. In contrast, familial microhematuria with thin basement membranes is thought to result from heterozygous COL4A3/A4 mutations. This absolute separation may not always be true. Renal biopsies and molecular genetics were used to study microhematuric families in the Hellenic population we serve. The COL4A5 gene was studied by PCR and direct re-sequencing for new mutations, while PCR-RFLP was used to identify more carriers of known COL4A5 and COL4A3/A4 mutations. Molecular genetics in two undiagnosed microhematuric Cypriot families, revealed COL4A5 mutation P628L indicating X-linked ATS. Of nine males, seven developed end stage kidney disease (ESKD) between 31 and 56, while two are well at 51 and 57, exhibiting microhematuria and thin basement membrane nephropathy (TBMN). COL4A5 mutation G624D was also identified in six Greek families. Seventy five members had DNA tests and 37 proved positive. Four positive males developed ESKD at 61, 51, 50 and 39 years, while the remaining and all females showed only microhematuria. A literature search revealed eight papers with six similar hypomorphic COL4A5 mutations presenting as phenocopies of TBMN. In conclusion, X-linked COL4A5 ATS mutations produce a phenotypic spectrum with a) classical ATS with early onset ESKD, neurosensory deafness and ocular defects b) males with only ESKD and late deafness and c) males due to missense mutations, such as G624D and P628L that may only exhibit microhematuria, TBMN, mild chronic renal failure (CRF) or late onset ESKD. Consequently when investigating "benign familial hematuria" these and other similar X-linked COL4A5 mutations should also be searched for.
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Affiliation(s)
- A Pierides
- Department of Nephrology, Hippocrateon Hospital, Nicosia, Cyprus ; Department of Biological Sciences and Molecular Medicine Research Center, University of Cyprus, Nicosia, Cyprus
| | - K Voskarides
- Department of Biological Sciences and Molecular Medicine Research Center, University of Cyprus, Nicosia, Cyprus
| | - M Kkolou
- Department of Nephrology, Larnaca General Hospital, Larnaca, Cyprus
| | - M Hadjigavriel
- Department of Nephrology, Larnaca General Hospital, Larnaca, Cyprus
| | - C Deltas
- Department of Biological Sciences and Molecular Medicine Research Center, University of Cyprus, Nicosia, Cyprus
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Yao XD, Chen X, Huang GY, Yu YT, Xu ST, Hu YL, Wang QW, Chen HP, Zeng CH, Ji DX, Hu WX, Tang Z, Liu ZH. Challenge in pathologic diagnosis of Alport syndrome: evidence from correction of previous misdiagnosis. Orphanet J Rare Dis 2012; 7:100. [PMID: 23259488 PMCID: PMC3552947 DOI: 10.1186/1750-1172-7-100] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 11/30/2012] [Indexed: 12/03/2022] Open
Abstract
Background Pathologic studies play an important role in evaluating patients with Alport syndrome besides genotyping. Difficulties still exist in diagnosing Alport syndrome (AS), and misdiagnosis is a not-so-rare event, even in adult patient evaluated with renal biopsy. Methods We used nested case–control study to investigate 52 patients previously misdiagnosed and 52 patients initially diagnosed in the China Alport Syndrome Treatments and Outcomes Registry e-system. Results We found mesangial proliferative glomerulonephritis (MsPGN, 26.9%) and focal and segmental glomerulosclerosis (FSGS, 19.2%) were the most common misdiagnosis. FSGS was the most frequent misdiagnosis in female X-linked AS (fXLAS) patients (34.8%), and MsPGN in male X-linked AS (mXLAS) patients (41.2%). Previous misdiagnosed mXLAS patients (13/17, 76.5%) and autosomal recessive AS (ARAS) patients (8/12, 66.7%) were corrected after a second renal biopsy. While misdiagnosed fXLAS patients (18/23, 78.3%) were corrected after a family member diagnosed (34.8%) or after rechecking electronic microscopy and/or collagen-IV alpha-chains immunofluresence study (COL-IF) (43.5%) during follow-up. With COL-IF as an additional criterion for AS diagnosis, we found that patients with less than 3 criteria reached have increased risk of misdiagnosis (3.29-fold for all misdiagnosed AS patients and 3.90-fold for fXLAS patients). Conclusion We emphasize timely and careful study of electronic microscopy and COL-IF in pathologic evaluation of AS patients. With renal and/or skin COL-IF as additional criterion, 3 diagnosis criteria reached are the cutoff for diagnosing AS pathologically.
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Affiliation(s)
- Xiao-Dan Yao
- Research Institute of Nephrology, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China.
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Glomerular pathology in Alport syndrome: a molecular perspective. Pediatr Nephrol 2012; 27:885-90. [PMID: 21455721 PMCID: PMC3484979 DOI: 10.1007/s00467-011-1868-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 03/09/2011] [Accepted: 03/10/2011] [Indexed: 01/28/2023]
Abstract
We have known for some time that mutations in the genes encoding 3 of the 6 type IV collagen chains are the underlying defect responsible for both X-linked (where the COL4A5 gene is involved) and autosomal (where either COL4A3 or COL4A4 genes are involved) Alport syndrome. The result of these mutations is the absence of the sub-epithelial network of all three chains in the glomerular basement membrane (GBM), resulting, at maturity, in a type IV collagen GBM network comprising only α1(IV) and α2(IV) chains. The altered GBM functions adequately in early life. Eventually, there is onset of proteinuria associated with the classic and progressive irregular thickening, thinning, and splitting of the GBM, which culminates in end-stage renal failure. We have learned much about the molecular events associated with disease onset and progression through the study of animal models for Alport syndrome, and have identified some potential therapeutic approaches that may serve to delay the onset or slow the progression of the disease. This review focuses on where we are in our understanding of the disease, where we need to go to understand the molecular triggers that set the process in motion, and what emergent therapeutic approaches show promise for ameliorating disease progression in the clinic.
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Affiliation(s)
- Robert J Courtney
- Case Eye Institute, Oregon Health and Science University, Portland, OR 97239, USA
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