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Alport syndrome: About time—treating children with Alport syndrome

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Abstract

Can treatment delay end-stage renal disease in children with Alport syndrome? New guidelines have been provided based on our ability to identify individuals at risk of early-onset renal failure and on evidence for blockade of the renin - angiotensin system that has been derived from Alport patient registries, other renal diseases and animal studies.

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... In patients with HN who are at risk for early-onset renal failure, treatment with renin-angiotensin system blockade can delay the onset of end-stage renal disease. [14][15][16]. Also, the patients with isolated microscopic hematuria and thin GBM lesions are at risk for chronic kidney disease especially in the setting of other comorbidities, such as hypertension. ...
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Hereditary nephritis (HN) and thin glomerular basement membrane (GBM) lesion share a common clinical presentation of persistent hematuria, thin GBM by kidney biopsy electron microscopic examination, and a mutation in type IV collagen. However, the clinical course and treatment for these entities are different with varying patterns of heredity. Ultrastructural examination of a renal biopsy specimen is essential for the morphologic diagnosis of HN and thin GBM lesion, whereas light microscopy may only give limited diagnostic clues. Additional workup including immunostaining for subtypes of type IV collagen may provide further information on underlying genetic mutations. The diagnosis of HN may lead to treatment with renin-angiotensin system blockade in patients at risk of early-onset renal failure to delay progression to end-stage renal disease. Additionally, patients with isolated microscopic hematuria and thin GBM lesion are at increased risk for chronic kidney disease when associated with other comorbidities; those patients should receive regular clinical assessment to prevent renal function decline.
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Introduction: Alport syndrome is a genetic disorder of basement membranes caused by mutations in the type IV collagen genes COL4A3, COL4A4 and COL4A5. The Alport phenotype includes progressive hematuric nephropathy often leading to end-stage renal disease (ESRD), sensorineural deafness and ocular lesions. Results of laboratory and clinical research studies form the basis for current treatment recommendations aimed at delaying ESRD and indicate novel therapeutic approaches that may prevent ESRD altogether in many affected individuals.Areas covered: This review of Alport syndrome therapeutics begins with a summary of current understanding of pathogenetic mechanisms, followed by discussion of intervention targeting tubular injury and interstitial fibrosis, cell-based therapies, modulation of glomerular signaling and gene delivery and manipulation. A PubMed search using the term ‘Alport syndrome’ was used to gather literature for this monograph.Expert opinion: Experimental and clinical data support the early initiation of ACE inhibition to delay the onset of ESRD. Novel therapies targeting disease pathways activated by type IV collagen deficiency in basement membranes have the potential to further improve outcomes, especially in patients with genotypes associated with relatively rapid loss of renal function.
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In this post hoc, secondary analysis of the Ramipril Efficacy In Nephropathy (REIN) trial, an angiotensin-converting enzyme (ACE) inhibition risk/benefit profile was assessed in 322 patients with nondiabetic, proteinuric chronic nephrop-athies and different degrees of renal insufficiency. The rate of GFR decline (GFR) and the incidence of end-stage renal disease (ESRD) during ramipril or non–ACE inhibitor treatment were compared within three tertiles of basal GFR. GFR was comparable in the three tertiles, whereas the incidence of ESRD was higher in the lowest tertile than in the middle and highest tertiles. Ramipril decreased GFR by 22%, 22%, and 35% and the incidence of ESRD by 33% (P 0.05), 37%, and 100% (P 0.01) in the lowest, middle, and highest tertiles, respectively. GFR reduction was predicted by basal systolic (P 0.0001), diastolic (P 0.02), and mean (P 0.001) BP and proteinuria (P 0.0001) but not by basal GFR (P 0.12). ESRD risk reduction was predicted by basal proteinuria (P 0.01) and GFR (P 0.0001) and was strongly dependent on treatment duration (P 0.0001). Adverse events were comparable among the three tertiles and within each tertile in the two treatment groups. Thus, disease progression and response to ACE inhibition do not depend on severity of renal insuf-ficiency. The risk of ESRD and the absolute number of events saved by ACE inhibition is highest in patients with the lowest GFR. However, renoprotection is maximized when ACE inhibition is started earlier and when long-lasting treatment may result in GFR stabilization and definitive prevention of ESRD.
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Background In diabetic nephropathy, angiotensin-converting-enzyme (ACE) inhibitors have a greater effect than other antihypertensive drugs on proteinuria and the progressive decline in glomerular filtration rate (GFR). Whether this difference applies to progression of nondiabetic proteinuric nephropathies is not clear. The Ramipril Efficacy In Nephropathy study of chronic nondiabetic nephropathies aimed to address whether glomerular protein traffic influences renal-disease progression, and whether an ACE inhibitor was superior to conventional treatment, with the same blood-pressure control, in reducing proteinuria, limiting GFR decline, and preventing endstage renal disease. Methods In this prospective double-blind trial, 352 patients were classified according to baseline proteinuria (stratum 1: 1-3 g/24 h; stratum 2: greater than or equal to 3 g/24 h), and randomly assigned ramipril or placebo plus conventional antihypertensive therapy targeted at achieving diastolic blood pressure under 90 mm Hg. The primary endpoint was the rate of GFR decline. Analysis was by intention to treat. Findings At the second planned interim analysis, the difference in decline in GFR between the ramipril and placebo groups in stratum 2 was highly significant (p=0.001). The Independent Adjudicating Panel therefore decided to open the randomisation code and do the final analysis in this stratum (stratum 1 continued in the trial). Data (at least three GFR measurements including baseline) were available for 56 ramipril-assigned patients and 61 placebo-assigned patients. The decline in GFR per month was significantly lower in the ramipril group than the placebo group (0.53 [0.08] vs 0.88 [0.13] mL/min, p=0.03). Among the ramipril-assigned patients, percentage reduction in proteinuria was inversely correlated with decline in GFR (p=0.035) and predicted the reduction in risk of doubling of baseline creatinine or endstage renal failure (18 ramipril vs 40 placebo, p=0.04). The risk of progression was still significantly reduced after adjustment for changes in systolic (p=0.04) and diastolic (p=0.04) blood pressure, but not after adjustment for changes in proteinuria. Blood-pressure control and the overall number of cardiovascular events were similar in the two treatment groups. Interpretation In chronic nephropathies with proteinuria of 3 g or more per 24 h, ramipril safely reduces proteinuria and the rate of GFR decline to an extent that seems to exceed the reduction expected for the degree of blood-pressure lowering.
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Background. Alport syndrome (AS) is a hereditary nephropathy characterized by progressive renal failure, hearing loss and ocular lesions. Numerous mutations of the COL4A5 gene encoding the α5‐chain of type IV collagen have been described, establishing the molecular cause of AS. The goal of the present study was to identify the genotype–phenotype correlations that are helpful in clinical counseling. COL4A5‐mutations (n=267) in males were analysed including 23 German Alport families. Methods. Exons of the COL4A5 gene were PCR‐amplified and screened by Southern blot, direct sequencing or denaturing gradient gel electrophoresis. Phenotypes were obtained by questionnaires or extracted from 44 publications in the literature. Data were analysed by Kaplan–Meier statistics, χ² and Kruskal–Wallis tests. Results. Genotype–phenotype data for 23 German Alport families are reported. Analysis of these data and of mutations published in the literature showed the type of mutation being a significant predictor of end‐stage renal failure (ESRF) age. The patients' renal phenotypes could be grouped into three cohorts: (1) large rearrangements, frame shift, nonsense, and splice donor mutations had a mean ESRF age of 19.8±5.7 years; (2) non‐glycine‐ or 3′ glycine‐missense mutations, in‐frame deletions/insertions and splice acceptor mutations had a mean ESRF age of 25.7±7.2 years and fewer extrarenal symptoms; (3) 5′ glycine substitutions had an even later onset of ESRF at 30.1±7.2 years. Glycine‐substitutions occurred less commonly de novo than all other mutations (5.5% vs 13.9%). However, due to the evolutionary advantage of their moderate phenotype, they were the most common mutations. The intrafamilial phenotype of an individual mutation was found to be very consistent with regards to the manifestation of deafness, lenticonus and the time point of onset of ESRF. Conclusions. Knowledge of the mutation adds significant information about the progress of renal and extrarenal disease in males with X‐linked AS. We suggest that the considerable prognostic relevance of a patient's genotype should be included in the classification of the Alport phenotype.
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We present clinical practice recommendations for the treatment of children with Alport syndrome who are not enrolled in clinical trials. Our goal is to promote early initiation of a standard therapeutic approach that will facilitate assessment of the safety and efficacy of the protocol. The treatment protocol is based on the reduction of proteinuria, intraglomerular pressure, and renal fibrosis via interference with the renin-angiotensin-aldosterone system.
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Alport syndrome inevitably leads to end-stage renal disease and there are no therapies known to improve outcome. Here we determined whether angiotensin-converting enzyme inhibitors can delay time to dialysis and improve life expectancy in three generations of Alport families. Patients were categorized by renal function at the initiation of therapy and included 33 with hematuria or microalbuminuria, 115 with proteinuria, 26 with impaired renal function, and 109 untreated relatives. Patients were followed for a period whose mean duration exceeded two decades. Untreated relatives started dialysis at a median age of 22 years. Treatment of those with impaired renal function significantly delayed dialysis to a median age of 25, while treatment of those with proteinuria delayed dialysis to a median age of 40. Significantly, no patient with hematuria or microalbuminuria advanced to renal failure so far. Sibling pairs confirmed these results, showing that earlier therapy in younger patients significantly delayed dialysis by 13 years compared to later or no therapy in older siblings. Therapy significantly improved life expectancy beyond the median age of 55 years of the no-treatment cohort. Thus, Alport syndrome is treatable with angiotensin-converting enzyme inhibition to delay renal failure and therapy improves life expectancy in a time-dependent manner. This supports the need for early diagnosis and early nephroprotective therapy in oligosymptomatic patients.
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Alport syndrome (AS) is a type IV collagen hereditary disease characterized by the association of progressive hematuric nephritis, hearing loss, and, frequently, ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease. Considerable allelic heterogeneity has been observed. A "European Community Alport Syndrome Concerted Action" has been established to delineate accurately the AS phenotype and to determine genotype-phenotype correlations in a large number of families. Data concerning 329 families, 250 of them with an X-linked transmission, were collected. Characteristics of the 401 male patients belonging to the 195 families with COL4A5 mutation are presented. All male patients were hematuric, and the rate of progression to end-stage renal failure and deafness was mutation-dependent. Large deletions, non-sense mutations, or small mutations changing the reading frame conferred to affected male patients a 90% probability of developing end-stage renal failure before 30 yr of age, whereas the same risk was of 50 and 70%, respectively, in patients with missense or splice site mutation. The risk of developing hearing loss before 30 yr of age was approximately 60% in patients with missense mutations, contrary to 90% for the other types of mutations. The natural history of X-linked AS and correlations with COL4A5 mutations have been established in a large cohort of male patients. These data could be used for further evaluation of therapeutic approaches.
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Full-text available
Alport syndrome (AS) is a hereditary nephropathy characterized by progressive renal failure, hearing loss and ocular lesions. Numerous mutations of the COL4A5 gene encoding the alpha 5-chain of type IV collagen have been described, establishing the molecular cause of AS. The goal of the present study was to identify the genotype-phenotype correlations that are helpful in clinical counseling. COL4A5-mutations (n=267) in males were analysed including 23 German Alport families. Exons of the COL4A5 gene were PCR-amplified and screened by Southern blot, direct sequencing or denaturing gradient gel electrophoresis. Phenotypes were obtained by questionnaires or extracted from 44 publications in the literature. Data were analysed by Kaplan-Meier statistics, chi(2) and Kruskal-Wallis tests. Genotype-phenotype data for 23 German Alport families are reported. Analysis of these data and of mutations published in the literature showed the type of mutation being a significant predictor of end-stage renal failure (ESRF) age. The patients' renal phenotypes could be grouped into three cohorts: (1) large rearrangements, frame shift, nonsense, and splice donor mutations had a mean ESRF age of 19.8+/-5.7 years; (2) non-glycine- or 3' glycine-missense mutations, in-frame deletions/insertions and splice acceptor mutations had a mean ESRF age of 25.7+/-7.2 years and fewer extrarenal symptoms; (3) 5' glycine substitutions had an even later onset of ESRF at 30.1+/-7.2 years. Glycine-substitutions occurred less commonly de novo than all other mutations (5.5% vs 13.9%). However, due to the evolutionary advantage of their moderate phenotype, they were the most common mutations. The intrafamilial phenotype of an individual mutation was found to be very consistent with regards to the manifestation of deafness, lenticonus and the time point of onset of ESRF. Knowledge of the mutation adds significant information about the progress of renal and extrarenal disease in males with X-linked AS. We suggest that the considerable prognostic relevance of a patient's genotype should be included in the classification of the Alport phenotype.
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X-linked hereditary nephritis (HN) in Samoyed dogs is a model for human HN (Alport's syndrome). Angiotensin converting enzyme (ACE) inhibitors have been shown to slow the progression of renal disease in animal models and human patients. To determine the effect of ACE inhibitor treatment on X-linked HN in Samoyed dogs, a group of affected and a group of normal males were each randomly divided into two subgroups, which were either treated with an ACE inhibitor or left untreated. ACE inhibitor treatment caused significant increases (P < 0.05) in plasma renin activity in normal and affected dogs, confirming its effectiveness, but did not lower systemic blood pressure. Three of four affected treated dogs had improved weight gains and, overall, treated dogs survived 1.36 times longer than affected untreated dogs (P < 0.05). ACE inhibitor treatment of affected dogs significantly delayed (P < 0.05) the onset of an increase in serum creatinine concentration, tended to delay the decline of glomerular filtration rate and effective renal plasma flow (ERPF), significantly improved (P < 0.05) the ERPF at 110-154 days of age, and significantly slowed (P < 0.01) the rate of increase of proteinuria. Affected treated dogs showed a significant (P < 0.05) transient reduction in glomerular basement membrane splitting. Thus, ACE inhibitor treatment of Samoyed dogs with X-linked HN produced beneficial effects with respect to renal function, renal structure, and survival.
Article
Alport syndrome (AS) is a common hereditary cause of end-stage renal failure in adolescence due to defects in type IV collagen genes. Molecular genetics allows early diagnosis, however, no preventive strategy can be offered. Using the COL4A3 -/- mouse, an animal model for human AS, we evaluated therapy with ramipril in mice. One hundred and twenty-two Alport-mice were treated with 10 mg/kg/day ramipril added to drinking water. Proteinuria, serum-urea and lifespan were monitored. Renal matrix was characterized by immunohistochemistry, light- and electron microscopy, and Western blot. Untreated COL4A3 -/- mice died from renal failure after 71 +/- 6 days. Early therapy starting at four weeks of age and continuing to death delayed onset and reduced the extent of proteinuria. Uremia was postponed by three weeks in treated animals. Lifespan increased by more than 100% to 150 +/- 21 days (P < 0.01). In parallel, decreased deposition of extracellular matrix and lessened interstitial fibrosis as well as reduced amounts of renal transforming growth factor-beta1 (TGF-beta1) could be demonstrated. Late therapy starting at seven weeks decreased proteinuria, however, lifespan did not increase significantly. The results indicate an antiproteinuric and antifibrotic nephroprotective effect of ramipril in COL4A3 -/- mice is mediated by down-regulation of TGF-beta1. This effect in mice is enhanced by initiation of therapy during pre-symptomatic disease. The data in COL4A3 -/- mice as an animal-model for Alport syndrome suggest that ramipril might as well delay renal failure in humans with AS. Early diagnosis and preemptive treatment also may be crucial in humans.
Article
Alport syndrome (AS) is a type IV collagen hereditary disease characterized by progressive hematuric nephritis, hearing loss, and ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease characterized by much less severe disease in girls and women. A "European Community Alport Syndrome Concerted Action" (ECASCA) group was established to delineate the Alport syndrome phenotype in each gender and to determine genotype-phenotype correlations in a large number of families. Data concerning 329 families, 250 of them with an X-linked transmission, were collected. Characteristics of heterozygous girls and women belonging to the 195 families with proven COL4A5 mutation are compared with those of hemizygous boys and men. Hematuria was observed in 95% of carriers and consistently absent in the others. Proteinuria, hearing loss, and ocular defects developed in 75%, 28%, and 15%, respectively. The probability of developing end-stage renal disease or deafness before the age of 40 yr was 12% and 10%, respectively, in girls and women versus 90 and 80%, respectively, in boys and men. The risk of progression to end-stage renal disease appears to increase after the age of 60 yr in women. Because of the absence of genotype-phenotype correlation and the large intrafamilial phenotypic heterogeneity, early prognosis of the disease in X-linked Alport syndrome carriers remains moot. Risk factors for developing renal failure have been identified: the occurrence and progressive increase in proteinuria, and the development of a hearing defect.
X-linked Alport syndrome: natural history in 195 families and genotype- phenotype correlations in males
  • J P Jais
  • JP Jais