Long-term treatment by ACE inhibitors and angiotensin receptor blockers in children with Alport syndrome

Case report: A novel compound heterozygous variant in the COL4A3 gene was identified in a patient with autosomal recessive Alport syndrome

Alport syndrome (AS), a hereditary kidney disease with a high risk for renal failure, is attributed to pathogenic variants in genes COL4A3, COL4A4, and COL4A5 that encode type IV collagen. Next-generation sequencing (NGS) is increasingly applied to the diagnosis of AS, but complex genotype-phenotype correlation, that is, identifying the significance of variants, is still a huge clinical challenge. In this study, we reported the case of a 27-year-old Chinese woman with a family history of hematuria and proteinuria. Notably, the proband is the only one in her family with renal insufficiency. NGS was performed in this family, and it was revealed that the proband was a compound heterozygote for two variants in the COL4A3 gene: c.2990G>A inherited from her father and c.4981C>T inherited from her mother. We modeled the spatial structure of the corresponding protein and assumed that structural abnormalities led to the breakdown of type IV collagen networks, a major component of the glomerular basement membrane. Thus, the proband was diagnosed with autosomal recessive AS, characterized by severe defects of the glomerular basement membrane. Hence, the proband showed a loss of renal function. This case presentation emphasizes the importance of NGS for AS diagnosis and introduces a novel genotype of AS.

Inherited causes of combined vision and hearing loss: clinical features and molecular genetics

Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.

Renin angiotensin aldosterone inhibitors in the treatment of proteinuria in children with congenital anomalies of the kidney and urinary tract: more evidence needed

INTRODUCTION

Congenital anomalies of the kidney and urinary tract (CAKUT) can be associated with proteinuria, possibly leading to a decline in kidney function. The aim of this review is to evaluate evidence on the efficacy of renin-angiotensin-aldosterone system inhibitors (RAASi) in children affected by CAKUT with proteinuria or chronic kidney disease (CKD).

AREAS COVERED

We conducted a bibliographic search between 1 December 2022 and 20 February 2023, including randomized controlled trials, case-control studies, observational studies, meta-analyses, and systematic reviews dealing with the efficacy of RAASi in reducing proteinuria and slowing the decline of kidney function in children.

EXPERT OPINION

RAASi are effective in reducing proteinuria and slowing CKD progression in many renal conditions; however, the efficacy of these drugs in patients affected by CAKUT with proteinuria is still unknown. While waiting for more evidence, when facing a child with CAKUT with isolated proteinuria or with proteinuria and CKD, a 6-12-month trial with RAASi with gradual increase to the maximal tolerated dose should be considered. If no improvement of proteinuria is obtained, the RAASi should be discontinued.

Single, Double and Triple Blockade of RAAS in Alport Syndrome: Different Tools to Freeze the Evolution of the Disease

Background: The goal of the treatment of Alport syndrome (AS) is to delay the progression of kidney damage. The current standard of care is the use of Renin Angiotensin Aldosterone System (RAAS) blockers: angiotensin-converting enzyme inhibition (ACEi), angiotensin receptor blockade, and, recently, spironolactone (SP). Aim of the study: the purpose of this retrospective study is to evaluate the efficacy (reduction of proteinuria and changes of glomerular function) and safety of a sequential introduction of RAAS blockers up to a triple RAAS blockade in pediatric proteinuric patients with AS. Methods: in this retrospective study (1995 to 2019), we evaluated proteinuria values in AS patients, during the 12 months following the beginning of a new RAAS blocker, up to a triple blockade. ACEi was always the first line of treatment; then ARB and SP were sequentially added if uPCR increased by 50% from the basal level in 2 consecutive samples during a 3-months observation period, or when uPCR ratio was >2 mg/mg. Results: 26 patients (mean age at treatment onset was 10.55 ± 5.02 years) were enrolled. All patients were on ACEi, 14/26 were started on a second drug (6/14 ARB, 8/14 SP) after a mean time of 2.2 ± 1.7 years, 7/26 were on triple RAAS blockade after a further period of 5.5 ± 2.3 years from the introduction of a second drug. Repeated Measure Anova analysis of log-transformed data shows that the reduction of uPCR values after Time 0 from the introduction of the first, second and third drug is highly significant in all three cases (p values = 0.0016, 0.003, and 0.014, respectively). No significant changes in eGFR were recorded in any group, apart from a 15-year-old boy with X-linked AS, who developed kidney failure. One patient developed mild hyperkaliemia, and one gynecomastia and symptomatic hypotension. No life-threatening events were recorded. Conclusions: double and triple RAAS blockade is an effective and safe strategy to reduce proteinuria in children with AS. Nevertheless, we suggest monitoring eGFR and Kaliemia during follow-up.

Organoprotective Effects of Spironolactone on Top of Ramipril Therapy in a Mouse Model for Alport Syndrome

Angiotensin-converting enzyme inhibitors (ACEi) delay progression of the inherited renal disease Alport syndrome. However, the effect of ACEis weakens gradually due to an “aldosterone escape”. Here, we investigate if an aldosterone antagonist can counteract loss of ACEi-efficacy. COL4A3−/− mice were treated with ramipril (ACEi), starting at 4.5 weeks of age, and spironolactone was added at 7 weeks of age. Lifespan until renal failure, as well as kidney function parameters, were investigated. Dual therapy decreased proteinuria levels compared to ACEi monotherapy. Matrix accumulation, as well as tubulointerstitial and glomerular scar-tissue formation, were significantly reduced compared to untreated mice and ACEi-monotherapy at 75 and 100 days. Lifespan in dual treated mice was extended compared to untreated mice. However, lifespan was not superior to ACEi monotherapy–despite improved urea-nitrogen levels in the dual therapy group. In conclusion, adding the aldosterone-antagonist spironolactone to ACEi therapy further improved kidney function and reduced proteinuria and fibrosis. However, survival was not improved further, possibly due to premature death from side effects of dual therapy such as hyperkalemia. Thus, dual therapy could offer an effective therapy option for Alport syndrome patients with progressive proteinuria. However, the risks of adverse events require close monitoring.

Genotype-phenotype correlations and nephroprotective effects of RAAS inhibition in patients with autosomal recessive Alport syndrome

BACKGROUND

Autosomal recessive Alport syndrome (ARAS) is caused by pathogenic variants in both alleles of either COL4A3 or COL4A4 genes. Reports on ARAS are rare due to small patient numbers and there are no reports on renin-angiotensin-aldosterone system (RAAS) inhibition therapy in ARAS.

METHODS

Retrospective study in 101 patients with ARAS from Chinese Registry Database of Hereditary Kidney Diseases and European Alport Registry. Genotype-phenotype correlations and nephroprotective effects of RAAS inhibition in ARAS were evaluated.

RESULTS

Median age was 15 years (range 1.5-46 years). Twelve patients progressed to stage 5 chronic kidney disease (CKD5) at median age 20.5 years. Patients without missense variants had both higher prevalence and earlier onset age of hearing loss, nephrotic-range proteinuria, more rapid decline of eGFR, and earlier onset age of CKD5 compared to patients with 1 or 2 missense variants. Most patients (79/101, 78%) currently are treated with RAAS inhibitors; median age at therapy initiation was 10 years and mean duration 6.5 ± 6.0 years. Median age at CKD5 for untreated patients was 24 years. RAAS inhibition therapy delayed CKD5 onset in those with impaired kidney function (T-III) to median age 35 years, but is undefined in treated patients with proteinuria (T-II) due to low number of events. No treated patients with microalbuminuria (T-I) progressed to CKD5. ARAS patients with 1 or 2 missense variants showed better response to treatment than patients with non-missense-variants.

CONCLUSIONS

Our study provides the first evidence for early use of RAAS inhibition therapy in patients with ARAS. Furthermore, genotype in ARAS correlates with response to therapy in favor of missense variants.

Genotype-phenotype correlations influence the response to angiotensin-targeting drugs in Japanese patients with male X-linked Alport syndrome

Early kidney failure in the hereditary type IV collagen disease, Alport syndrome, can be delayed by renin-angiotensin inhibitors. However, whether all patients and all different genotypes respond equally well to this kidney-protective therapy remains unclear. Here, we performed a retrospective study on 430 patients with male X-linked Alport syndrome to examine the relationships among kidney prognosis, genotype, and treatment effect in a large cohort of Japanese patients. We analyzed the clinical features, genotype-phenotype correlation, and kidney survival period for patients treated with or without renin-angiotensin inhibitors. As a result, the median kidney survival period of patients in this cohort was found to be at 35 years with a strong genotype-phenotype correlation. The median age at the onset of end stage kidney disease (ESKD) significantly differed between patients treated with and without renin-angiotensin inhibitors (over 50 years versus 28 years, respectively). Moreover, these drugs delayed the onset of ESKD in patients with truncating variants for 12 years, extending the median age from 16 years to 28 years. Thus, our results confirmed a strong genotype-phenotype correlation in patients with male X-linked Alport syndrome. Additionally, it was suggested that renin-angiotensin inhibitors could significantly delay ESKD progression. Despite these therapies, patients with truncating variants developed ESKD at the median age of 28 years.

An overview of the multi-pronged approach in the diagnosis of Alport syndrome for 22 children in Northeast China

BACKGROUND

Alport syndrome (AS) is a kind of progressive hereditary nephritis induced by mutations of different genes that encode collagen IV. The affected individuals usually develop hematuria during childhood, accompanying with gradual deterioration of renal functions. In this study, the multi-pronged approach was employed to improve the diagnosis of AS.

METHODS

Twenty-two children were diagnosed and treated at the Department of Pediatric Nephrology of Jilin University First Hospital between January 2017 and January 2020 using the multi-pronged approach. The following information was collected from patients, including age of onset, age at diagnosis, clinical manifestations, family history, renal pathology and genotype.

RESULTS

All these 22 children were diagnosed with Alport syndrome according to the diagnostic criteria formulated by the Japanese Society of Nephrology (2015), among them, only 13 children met the diagnostic criteria released in 1988. All the 22 patients presented with hematuria, and proteinuria to varying degrees was observed in some patients. Three children suffered from hearing loss, but no child in the cohort had any visual problem or renal failure. Meanwhile, five patients were estimated to be at Stage 2, whereas the remaining 17 cases were at Stage 0. Renal biopsies were performed in 18 patients, including 14 showing glomerular basement membranes (GBM)-specific abnormalities. Moreover, 13 children were detected with mutations of genes encoding collagen IV.

CONCLUSIONS

The multi-pronged approach helps to improve the diagnosis of AS. Most patients do not have renal failure during childhood, but close assessment and monitoring are necessary. Also, the advancements in treatment are reviewed.

Should ACE inhibitors and ARBs be used in combination in children?

The renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in a host of renal and cardiovascular functions. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), drugs that disrupt RAAS function, are effective in treating hypertension and offer other renoprotective effects independent of blood pressure (BP) reduction. As our understanding of RAAS physiology and the feedback mechanisms of ACE inhibition and angiotensin receptor blockade have improved, questions have been raised as to whether combination ACEI/ARB therapy is warranted in certain patients with incomplete angiotensin blockade on one agent. In this review, we discuss the rationale for combination ACEI/ARB therapy and summarize the results of key adult studies and the limited pediatric literature that have investigated this therapeutic approach. We additionally review novel therapies that have been developed over the past decade as alternative approaches to combination ACEI/ARB therapy, or that may be potentially used in combination with ACEIs or ARBs, in which further adult and pediatric studies are needed.

A case report of thin basement membrane nephropathy accompanied by sporadic glomerulocystic kidney disease

Background

Thin basement membrane nephropathy (TBMN) is a relatively common disease. Patients typically present with isolated hematuria, which has a good renal prognosis. In contrast, glomerulocystic kidney disease (GCKD) is a rare disease, associated with slow progressive renal dysfunction. To our knowledge, co-occurring diagnosis of TBMN with GCKD has not been reported previously.

Case presentation

A 30-year old woman was admitted to our hospital for evaluation of hematuria and renal insufficiency. Upon examination, her urinary protein level was 40 mg/day and occult blood in her urine was 2+. The patient’s urinary dysmorphic red blood cell sediment was 30–49/high power field. In contrast, her serum creatinine levels increased from 0.57 mg/dl to 0.86 mg/dl during the previous 2-years, without special events. She suffered from far-sightedness and astigmatism beginning at birth; She had no family history of renal disease. Renal biopsy demonstrated cystic dilatation of the Bowman’s capsule and atrophy of the glomerular tuft. The glomerular basement membrane (GBM) was thin, with an average thickness of 191 nm. Next-generation sequencing was used to evaluate for mutations in COL4A3 and COL4A4, associated with TBMN, and UMOD, MUC1, and SEC61A1, associated with hereditary GCKD. No pathogenic mutations were identified. We thus diagnosed the patient with TBMN coexistent with sporadic GCKD.

Conclusion

We report the patient diagnosed with TBMN accompanied by sporadic GCKD, based on renal biopsy and genetic testing. Because it is possible that other diseases, such as GCKD, can coexist with TBMN, it is important to consider renal biopsy.

Novel mutations in patients with X-linked Alport syndrome: Two case reports

RATIONALE

A genotype-phenotype correlation is known to be associated with Alport syndrome (AS). Identifying novel mutations can expand the knowledge about the natural course of AS.

PATIENT CONCERNS

The first patient was a-15-year-old boy detected with proteinuria during the school health check-up. The second case was a-29-year-old woman, who visited the outpatient clinic for edema.

DIAGNOSIS

We performed targeted next-generation sequencing to identify the mutations associated with AS. Results were confirmed by Sanger sequencing and multiplex ligation-dependent probe amplification. Missense mutation (c.2332G>C, p.Gly778Arg) was identified in the first case and an exon 16 deletion was also identified in the second case.

INTERVENTION

We treated both cases with angiotensin receptor blocker (ARB).

OUTCOMES

The amount of proteinuria in the first case did not change after ARB therapy, during the follow-up period (1 year). Proteinuria in the woman decreased to half of the baseline level, 1 year after treatment. Glomerular filtration rate was also maintained during the follow-up.

CONCLUSION

We identified novel mutations in Koreans with an X-linked AS mutation in the COL4A5 gene and an individual phenotype. This is the first report of AS patients with a novel missense mutation and copy number variation.

Advances in molecular diagnosis and therapeutics in nephrotic syndrome and focal and segmental glomerulosclerosis

PURPOSE OF REVIEW

The widespread adoption of next-generation sequencing by research and clinical laboratories has begun to uncover the previously unknown genetic basis of many diseases. In nephrology, one of the best examples of this is seen in focal and segmental glomerulosclerosis (FSGS) and nephrotic syndrome. We review advances made in 2017 as a result of human and molecular genetic studies as it relates to FSGS and nephrotic syndrome.

RECENT FINDINGS

There are more than 50 monogenic genes described in steroid-resistant nephrotic syndrome and FSGS, with seven reported in 2017. In individuals presenting with FSGS or nephrotic syndrome before or at the age of 18 years, the commonest genes in which a mutation is found continues to be limited to only a few including NPHS1 and NPHS2 based on multiple studies. For FSGS or nephrotic syndrome that presents after 18 years, mutations in COl4A3/4/5, traditionally associated with Alport syndrome, are increasingly being reported. Despite the extensive genetic heterogeneity in FSGS, there is evidence that some of these genes converge onto common pathways. There are also reports of in-vivo models exploring apolipoprotein 1 biology, variants in which account for part of the increased risk of nondiabetic kidney disease in African-Americans. Finally, genetic testing has several clinical uses including clarification of diagnosis and treatment; identification of suitable young biologic relatives for kidney donation; and preimplantation genetic diagnosis. CRISPR gene editing is currently an experimental tool only, but the recent reports of excising mutations in embryos could be a therapeutic option for individuals with any monogenic disorder in the future.

SUMMARY

Sequencing efforts are bringing novel variants into investigation and directing the efforts to understand how these lead to disease phenotypes. Expanding our understanding of the genetic basis of health and disease processes is the necessary first step to elaborate the repertoire of therapeutic agents available for patients with FSGS and nephrotic syndrome.

Renal, auricular, and ocular outcomes of Alport syndrome and their current management

Alport syndrome is a hereditary glomerular basement membrane disease caused by mutations in the COL4A3/4/5 genes encoding the type IV collagen alpha 3-5 chains. Most cases of Alport syndrome are inherited as X-linked dominant, and some as autosomal recessive or autosomal dominant. The primary manifestations are hematuria, proteinuria, and progressive renal failure, whereas some patients present with sensorineural hearing loss and ocular abnormalities. Renin-angiotensin-aldosterone system blockade is proven to delay the onset of renal failure by reducing proteinuria. Renal transplantation is a curative treatment for patients who have progressed to end-stage renal disease. However, only supportive measures can be used to improve hearing loss and visual loss. Although both stem cell therapy and gene therapy aim to repair the basement membrane defects, technical difficulties require more research in Alport mice before clinical studies. Here, we review the renal, auricular, and ocular manifestations and outcomes of Alport syndrome and their current management.

Accelerated podocyte detachment and progressive podocyte loss from glomeruli with age in Alport Syndrome

Podocyte depletion is a common mechanism driving progression in glomerular diseases. Alport Syndrome glomerulopathy, caused by defective α3α4α5 (IV) collagen heterotrimer production by podocytes, is associated with an increased rate of podocyte detachment detectable in urine and reduced glomerular podocyte number suggesting that defective podocyte adherence to the glomerular basement membrane might play a role in driving progression. Here a genetically phenotyped Alport Syndrome cohort of 95 individuals [urine study] and 41 archived biopsies [biopsy study] were used to test this hypothesis. Podocyte detachment rate (measured by podocin mRNA in urine pellets expressed either per creatinine or 24-hour excretion) was significantly increased 11-fold above control, and prior to a detectably increased proteinuria or microalbuminuria. In parallel, Alport Syndrome glomeruli lose an average 26 podocytes per year versus control glomeruli that lose 2.3 podocytes per year, an 11-fold difference corresponding to the increased urine podocyte detachment rate. Podocyte number per glomerulus in Alport Syndrome biopsies is projected to be normal at birth (558/glomerulus) but accelerated podocyte loss was projected to cause end-stage kidney disease by about 22 years. Biopsy data from two independent cohorts showed a similar estimated glomerular podocyte loss rate comparable to the measured 11-fold increase in podocyte detachment rate. Reduction in podocyte number and density in biopsies correlated with proteinuria, glomerulosclerosis, and reduced renal function. Thus, the podocyte detachment rate appears to be increased from birth in Alport Syndrome, drives the progression process, and could potentially help predict time to end-stage kidney disease and response to treatment.