The PROPKD Score: A New Algorithm to Predict Renal Survival in Autosomal Dominant Polycystic Kidney Disease

Somatic mutation in autosomal dominant polycystic kidney disease revealed by deep sequencing human kidney cysts

Autosomal Dominant Polycystic Kidney Disease (ADPKD) results in progressive cysts that lead to kidney failure, and is caused by heterozygous germline variants in PKD1 or PKD2. Cyst pathogenesis is not definitively understood. Somatic second-hit mutations have been implicated in cyst pathogenesis, though technical sequencing challenges have limited investigation. We used unique molecular identifiers, high-depth massively parallel sequencing and custom analysis techniques to identify somatic second-hit mutations in 24 whole cysts from disparate regions of six human ADPKD kidneys, utilising replicate samples and orthogonal confirmation. Average depth of coverage of 1166 error-corrected reads for PKD1 and 539 reads for PKD2 was obtained. 58% (14/24) of cysts had a detectable PKD1 somatic variant, with 5/6 participants having at least one cyst with a somatic variant. We demonstrate that low-frequency somatic mutations are detectable in a proportion of cysts from end-stage ADPKD human kidneys. Further studies are required to understand the drivers of this somatic mutation.

Recommendations for European laboratories based on the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease

The 2024 Kidney Disease: Improving Global Outcomes (KDIGO) guidelines for chronic kidney disease (CKD) evaluation and management bring important updates, particularly for European laboratories. These guidelines emphasize the need for harmonization in CKD testing, promoting the use of regional equations. In Europe, the European Kidney Function Consortium (EKFC) equation is particularly suited for European populations, particularly compared to the CKD-EPI 2021 race-free equation. A significant focus is placed on the combined use of creatinine and cystatin C to estimate glomerular filtration rate (eGFRcr-cys), improving diagnostic accuracy. In situations where eGFR may be inaccurate or clinically insufficient, the guidelines encourage the use of measured GFR (mGFR) through exogenous markers like iohexol. These guidelines emphasize the need to standardize creatinine and cystatin C measurements, ensure traceability to international reference materials, and adopt harmonized reporting practices. The recommendations also highlight the importance of incorporating risk prediction models, such as the Kidney Failure Risk Equation (KFRE), into routine clinical practice to better tailor patient care. This article provides a European perspective on how these KDIGO updates should be implemented in clinical laboratories to enhance CKD diagnosis and management, ensuring consistency across the continent.

KDOQI US Commentary on the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD

The Kidney Disease Outcomes Quality Initiative (KDOQI) convened a work group to review the 2024 KDIGO (Kidney Disease: Improving Global Outcomes) guideline for the management of chronic kidney disease (CKD). The KDOQI Work Group reviewed the KDIGO guideline statements and practice points and provided perspective for implementation within the context of clinical practice in the United States. In general, the KDOQI Work Group concurs with several recommendations and practice points proposed by the KDIGO guidelines regarding CKD evaluation, risk assessment, and management options (both lifestyle and medications) for slowing CKD progression, addressing CKD-related complications, and improving cardiovascular outcomes. The KDOQI Work Group acknowledges the growing evidence base to support the use of several novel agents such as sodium/glucose cotransporter 2 inhibitors for several CKD etiologies, and glucagon-like peptide 1 receptor agonists and nonsteroidal mineralocorticoid receptor antagonists for type 2 CKD in setting of diabetes. Further, KDIGO guidelines emphasize the importance of team-based care which was also recognized by the work group as a key factor to address the growing CKD burden. In this commentary, the Work Group has also assessed and discussed various barriers and potential opportunities for implementing the recommendations put forth in the 2024 KDIGO guidelines while the scientific community continues to focus on enhancing early identification of CKD and discovering newer therapies for managing kidney disease.

Progression to kidney failure in ADPKD: the PROPKD score underestimates the risk assessed by the Mayo imaging classification

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease and fourth leading cause for renal replacement therapy worldwide. Disease progression is tightly linked to genotype, however, factors like genetic modifiers and environmental factors are responsible for a high phenotypic variability within- as well as between families. Individual's risk of progression to kidney failure is assessed using prediction- or risk-assessment tools such as the predicting renal outcomes in ADPKD score (PROPKD score) and the Mayo Imaging Classification (MIC). The PROPKD score encompasses genetic and phenotypic parameters, while the MIC relies on renal imaging, height, and age of patients. Both methods categorize patients into low-risk, intermediate-risk, and high-risk for progression to kidney failure. In this retrospective, cross-sectional study, we calculated the risk of progression to kidney failure in our population and analyzed the agreement between the methods in three separate models with alternating stratification of MIC risk categories. We found a mismatch for risk assessment between the respective risk categories, indicating that the PROPKD score and MIC should not be used interchangeably. Preferably, the MIC should be used as a base for risk assessment and may be enhanced by genotypic and phenotypic information.

Autosomal Dominant Polycystic Kidney Disease

Over 50% of people affected with autosomal dominant polycystic kidney disease (ADPKD) will develop kidney failure, making ADPKD the 4th most common cause of end-stage kidney disease. ADPKD is a systemic condition affecting the kidneys, liver, heart, vasculature, and other organ systems. A minority of patients may have severe complications such as massive hepatomegaly from a polycystic liver or rupture of an intracranial aneurysm. Recent advances in the understanding of genetics, prognosis, and treatment of this condition have allowed delivery of personalized treatment capable of changing the natural history of the disease. This review focuses on diagnosis, determining risk of kidney failure, treatment, blood pressure management, and preimplantation genetic testing related to ADPKD.

A guide to gene-disease relationships in nephrology

The use of next-generation sequencing technologies such as exome and genome sequencing in research and clinical care has transformed our understanding of the molecular architecture of genetic kidney diseases. Although the capability to identify and rigorously assess genetic variants and their relationship to disease has advanced considerably in the past decade, the curation of clinically relevant relationships between genes and specific phenotypes has received less attention, despite it underpinning accurate interpretation of genomic tests. Here, we discuss the need to accurately define gene-disease relationships in nephrology and provide a framework for appraising genetic and experimental evidence critically. We describe existing international programmes that provide expert curation of gene-disease relationships and discuss sources of discrepancy as well as efforts at harmonization. Further, we highlight the need for alignment of disease and phenotype terminology to ensure robust and reproducible curation of knowledge. These collective efforts to support evidence-based translation of genomic sequencing into practice across clinical, diagnostic and research settings are crucial for delivering the promise of precision medicine in nephrology, providing more patients with timely diagnoses, accurate prognostic information and access to targeted treatments.

Treatment of Autosomal-Dominant Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is a chronic systemic disease that affects all races and ethnicities. It is the fourth leading cause of end-stage kidney disease, and it has a heterogenous phenotype ranging from mild to severe disease. Identifying patients with ADPKD who are at risk of rapid progression can guide therapeutic decisions. Several tools to predict disease severity are available, based on features such as total kidney volume assessed with magnetic resonance imaging, PKD genotype, estimated glomerular filtration rate (eGFR) trajectory, and the occurrence of hypertension and urologic complications early in life. During the past decade, more evidence has emerged regarding optimal ADPKD management. The HALT PKD (Halt Progression of Polycystic Kidney Disease) trial supported intensive blood pressure control in patients younger than 50 years of age with preserved kidney function. A healthy lifestyle, including maintaining a healthy weight, salt restriction, and smoking cessation, is likely to be beneficial. Tolvaptan, the only disease-modifying agent for patients with ADPKD at risk of rapid progression, is gaining wider use, but is still limited by its side effects. This is an exciting time for the ADPKD community because multiple promising interventions are in the pipeline and being investigated.

Kidney growth progression patterns in autosomal dominant polycystic kidney disease

BACKGROUND

Prognosis for autosomal dominant polycystic kidney disease (ADPKD), the main inherited cause of kidney failure, relies on estimating cystic growth using linear formulas derived from height-adjusted total kidney volume (Ht-TKV). However, nonlinear renal growth patterns may occur in typical ADPKD.

AIMS

To determine kidney outcomes of subjects diagnosed with typical ADPKD exhibiting nonlinear, and unpredictable cystic growth during follow-up.

METHODS

Retrospective cohort study. We categorized TKV changes in individuals with typical ADPKD according to observed kidney growth trajectories. Ht-TKV was calculated from consecutive CT or MRI using the ellipsoid method. We compared estimated glomerular filtration rate (eGFR) trajectories with linear mixed models.

RESULTS

We included 83 individuals with ADPKD (67% women; age 47 ± 12 years; follow-up 5.2 years [IQR 2.8-9.0]). Three kidney growth patterns were observed: slow progression (24%, <3%/year linear increase), fast progression (39%, ≥3%/year linear increase), and atypical progression (37%, nonlinear growth). Adjusted ht-TKV change in mL/m/year was +1.4 (IQR -4.5 to +10.0), +40.3 (+16.9 to +89.3), and +32.8 (+15.9 to +85.9) for slow, fast, and atypical progressors, respectively (p < 0.001). Atypical progressors exhibited a significantly greater decline in eGFR in mL/min/m²/year (-7.9, 95% CI -6.5, -3.9) compared to slow (-0.5, 95% CI -3.1 to +0.5) and fast progressors (-3.4, 95% CI -7.9, -2.0; between-group p < 0.001). Atypical progressors had a higher proportion of acute complications, including hemorrhages, infections, and urolithiasis (84%), compared to slow (20%) and fast progressors (31%) (p < 0.001).

CONCLUSION

In typical ADPKD, nonlinear, abrupt, and unpredictable cyst growth occurs frequently, leading to a higher risk of acute complications and kidney function decline.

Biomarkers of Kidney Disease Progression in ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disorder and the fourth leading cause of kidney failure (KF) in adults. Characterized by a reduction in glomerular filtration rate (GFR) and increased kidney size, ADPKD exhibits significant variability in progression, highlighting the urgent need for reliable and predictive biomarkers to optimize management and treatment approaches. This review explores the roles of diverse biomarkers-including clinical, genetic, molecular, and imaging biomarkers-in evaluating disease progression and customizing treatments for ADPKD. Clinical biomarkers such as biological sex, the predicting renal outcome in polycystic kidney disease (PROPKD) score, and body mass index are shown to correlate with disease severity and progression. Genetic profiling, particularly distinguishing between truncating and non-truncating pathogenic variants in the PKD1 gene, refines risk assessment and prognostic precision. Advancements in imaging significantly enhance our ability to assess disease severity. Height-adjusted total kidney volume (htTKV) and the Mayo imaging classification (MIC) are foundational, whereas newer imaging biomarkers, including texture analysis, total cyst number (TCN), cyst-parenchyma surface area (CPSA), total cyst volume (TCV), and cystic index, focus on detailed cyst characteristics to offer deeper insights. Molecular biomarkers (including serum and urinary markers) shed light on potential therapeutic targets that could predict disease trajectory. Despite these advancements, there is a pressing need for the development of response biomarkers in both the adult and pediatric populations, which can evaluate the biological efficacy of treatments. The holistic evaluation of these biomarkers not only deepens our understanding of kidney disease progression in ADPKD, but it also paves the way for personalized treatment strategies aiming to significantly improve patient outcomes.

New Mutation Associated with Polycystic Kidney Disease Type I: A Case Report

INTRODUCTION

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most prevalent heritable disorders, characterized by the progressive development of kidney cysts leading to renal failure. It is primarily caused by mutations in the PKD1 and PKD2 genes, which account for approximately 85% and 15% of cases, respectively. This case report describes a previously unreported mutation in the PKD1 gene, identified in a family involving an aunt and her niece with ADPKD.

CASE PRESENTATION

The index case, a 56-year-old female with chronic kidney disease stage 3b secondary to ADPKD and hypertension, exhibited a strong family history of polycystic kidney disease (PKD). Initial genetic evaluations did not identify any recognized pathogenic mutations, leading to a more detailed investigation which revealed a novel mutation in the PKD1 gene. This mutation was also found in her niece, who presented with early-onset disease.

CONCLUSIONS

The identification of a heterozygous six-nucleotide deletion, c.2084_2089del, resulting in the in-frame deletion of two amino acids, p.Pro695_Ala696del, in the PKD1 gene, has been linked with ADPKD in these patients. This report emphasizes the need for continuous updates to genetic data for a deeper understanding of the diagnosis and prognosis of ADPKD that could potentially aid in targeted therapy.

Association of hyperphosphatemia with renal prognosis in patients with autosomal dominant polycystic kidney disease

BACKGROUND

Serum phosphate (P) levels are generally lower in autosomal dominant polycystic kidney disease (ADPKD) than in other kidney disorders, potentially masking the clinical significance of hyperphosphatemia. This study aimed to determine if serum P levels can predict renal outcomes in ADPKD patients.

METHODS

We included 235 patients with ADPKD who were not taking drugs to treat hyperphosphatemia. Survival analysis was performed for the renal outcome of a 50% reduction in estimated glomerular filtration rate or initiation of renal replacement therapy.

RESULTS

Multivariable Cox regression analyses revealed that serum P (1 mg/dL increase, HR = 2.03, P < 0.0001) was a significant risk factor for kidney disease progression. Similarly, hyperphosphatemia (P > 3.5 mg/dL, HR = 2.05; P > 4.0 mg/dL, HR = 1.90; P > 4.5 mg/dL, HR = 2.78; P > 5.0 mg/dL, HR = 27.22) was significantly associated with renal prognosis. Kaplan-Meier analysis showed significantly lower kidney survival rates in patients with P > 3.5 mg/dL than in those without hyperphosphatemia (log-rank test, P < 0.0001), and similar Kaplan-Meier analysis results were found for P > 4.0 mg/dL, P > 4.5 mg/dL, and P > 5.0 mg/dL. The 2 year kidney survival rate for ADPKD patients with P > 3.5 mg/dL was 66.7% overall and 41.4% in those with stage 4-5 CKD. For patients with P > 4.0 mg/dL, the survival rate dropped to 46.8% overall and 28.2% in those with stage 4-5 CKD, indicating a very poor prognosis.

CONCLUSION

Hyperphosphatemia was associated with renal prognosis in patients with ADPKD. In these patients, attention should be paid to even mild serum P elevation of > 3.5 or > 4.0 mg/dL.

The Influence of Non-Pharmacological and Pharmacological Interventions on the Course of Autosomal Dominant Polycystic Kidney Disease

Polycystic kidney disease (PKD) includes autosomal dominant (ADPKD) and autosomal recessive (ARPKD) forms, both of which are primary genetic causes of kidney disease in adults and children. ADPKD is the most common hereditary kidney disease, with a prevalence of 329 cases per million in Europe. This condition accounts for 5-15% of end-stage chronic kidney disease (ESKD) cases, and in developed countries such as Poland, 8-10% of all dialysis patients have ESKD due to ADPKD. The disease is caused by mutations in the PKD1 and PKD2 genes, with PKD1 mutations responsible for 85% of cases, leading to a more aggressive disease course. Recent research suggests that ADPKD involves a metabolic defect contributing to cystic epithelial proliferation and cyst growth. Aim: This review explores the interplay between metabolism, obesity, and ADPKD, discussing dietary and pharmacological strategies that target these metabolic abnormalities to slow disease progression. Conclusion: Metabolic reprogramming therapies, including GLP-1 analogs and dual agonists of GIP/GLP-1 or glucagon/GLP-1 receptors, show promise, though further research is needed to understand their potential in ADPKD treatment fully.

Quantifying variant contributions in cystic kidney disease using national-scale whole-genome sequencing

BACKGROUNDCystic kidney disease (CyKD) is a predominantly familial disease in which gene discovery has been led by family-based and candidate gene studies, an approach that is susceptible to ascertainment and other biases.METHODSUsing whole-genome sequencing data from 1,209 cases and 26,096 ancestry-matched controls participating in the 100,000 Genomes Project, we adopted hypothesis-free approaches to generate quantitative estimates of disease risk for each genetic contributor to CyKD, across genes, variant types and allelic frequencies.RESULTSIn 82.3% of cases, a qualifying potentially disease-causing rare variant in an established gene was found. There was an enrichment of rare coding, splicing, and structural variants in known CyKD genes, with statistically significant gene-based signals in COL4A3 and (monoallelic) PKHD1. Quantification of disease risk for each gene (with replication in the separate UK Biobank study) revealed substantially lower risk associated with genes more recently associated with autosomal dominant polycystic kidney disease, with odds ratios for some below what might usually be regarded as necessary for classical Mendelian inheritance. Meta-analysis of common variants did not reveal significant associations, but suggested this category of variation contributes 3%-9% to the heritability of CyKD across European ancestries.CONCLUSIONBy providing unbiased quantification of risk effects per gene, this research suggests that not all rare variant genetic contributors to CyKD are equally likely to manifest as a Mendelian trait in families. This information may inform genetic testing and counseling in the clinic.

Genetic Analysis of Severe Polycystic Liver Disease in Japan

Key Points

Among patients with severe polycystic liver disease (PLD) (height-adjusted total liver volume of <1800 ml/m), PKD2 variants were found in 34%. Three patients with PKD1 or PKD2 variants are reported with severe PLD but normal-sized kidneys (hTKV of < 250 ml/m).

Background

Polycystic liver disease (PLD) is present in most patients with autosomal dominant polycystic kidney disease (ADPKD). PLD can alternatively be found with few, if any, kidney cysts as a diagnosis of isolated PLD (autosomal dominant PLD [ADPLD]). Several genes are identified as causative for this spectrum of phenotypes; however, the relative incidence of genetic etiologies among patients with severe PLD is unknown.

Methods

Patients with ADPKD or ADPLD having severe PLD defined as height-adjusted total liver volume (hTLV) >1800 ml/m were recruited. Subsequent clinical care was followed. Genetic analysis was performed using whole exome sequencing.

Results

We enrolled and sequenced 49 patients (38 women, 11 men). Pathogenic or suspected pathogenic variants in polycystic disease genes were found in 44 of 49 patients (90%). The disease gene was PKD1 in 20 of 44 patients (45%), PKD2 in 15 of 44 patients (34%), PRKCSH in 5 of 44 patients (11%), GANAB in 2 of 44 patients (5%), SEC63 in 1 of 44 patients (2%), and ALG8 in 1 of 44 patients (2%). The median hTLV was no different between genetically defined ADPKD and ADPLD groups (4431 [range, 1817–9148] versus 3437 [range, 1860–8211]) ml, P = 0.77), whereas height-adjusted kidney volume was larger as expected in ADPKD than in ADPLD (607 [range, 190–2842] versus 179 [range, 138–234] ml/m, P < 0.01). Of the clinically defined ADPKD patients, 20 of 38 patients (53%) were PKD1 , 15 of 38 (39%) were PKD2 , and 3 (8%) remained genetically unsolved. Among patients with a pathogenic PKD1 or PKD2 variant, we found three patients with a liver-dominant ADPKD (severe PLD with height-adjusted total kidney volume <250 ml/m).

Conclusions

ADPLD-related genes represent 20% of patients with severe PLD in our cohort. Of those enrolled with ADPKD, we observed a higher frequency of PKD2 carriers than in any previously reported ADPKD cohorts. Although there was no significant difference in the hTLV between patients with PKD1 and PKD2 in this cohort, our data suggest that enrollment on the basis of severe PLD may enrich for patients with PKD2 .

Quantitative susceptibility mapping for detection of kidney stones, hemorrhage differentiation, and cyst classification in ADPKD

BACKGROUND AND PURPOSE

The objective is to demonstrate feasibility of quantitative susceptibility mapping (QSM) in autosomal dominant polycystic kidney disease (ADPKD) patients and to compare imaging findings with traditional T1/T2w magnetic resonance imaging (MRI).

METHODS

Thirty-three consecutive patients (11 male, 22 female) diagnosed with ADPKD were initially selected. QSM images were reconstructed from the multiecho gradient echo data and compared to co-registered T2w, T1w, and CT images. Complex cysts were identified and classified into distinct subclasses based on their imaging features. Prevalence of each subclass was estimated.

RESULTS

QSM visualized two renal calcifications measuring 9 and 10 mm and three pelvic phleboliths measuring 2 mm but missed 24 calcifications measuring 1 mm or less and 1 larger calcification at the edge of the field of view. A total of 121 complex T1 hyperintense/T2 hypointense renal cysts were detected. 52 (43%) Cysts appeared hyperintense on QSM consistent with hemorrhage; 60 (49%) cysts were isointense with respect to simple cysts and normal kidney parenchyma, while the remaining 9 (7%) were hypointense. The presentation of the latter two complex cyst subtypes is likely indicative of proteinaceous composition without hemorrhage.

CONCLUSION

Our results indicate that QSM of ADPKD kidneys is possible and uniquely suited to detect large renal calculi without ionizing radiation and able to identify properties of complex cysts unattainable with traditional approaches.

Kidney phosphate wasting predicts poor outcome in polycystic kidney disease

BACKGROUND

Patients with autosomal dominant polycystic kidney disease (ADPKD) have disproportionately high levels of fibroblast growth factor 23 (FGF-23) for their chronic kidney disease stage, however only a subgroup develops kidney phosphate wasting. We assessed factors associated with phosphate wasting and hypothesize that it identifies patients with more severe disease and predicts disease progression.

METHODS

We included 604 patients with ADPKD from a multicenter prospective observational cohort (DIPAK; Developing Intervention Strategies to Halt Progression of Autosomal Dominant Polycystic Kidney Disease) in four university medical centers in the Netherlands. We measured parathyroid hormone (PTH) and total plasma FGF-23 levels, and calculated the ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR) with <0.8 mmol/L defined as kidney phosphate wasting. We analysed the association of TmP/GFR with estimated GFR (eGFR) decline over time and the risk for a composite kidney outcome (≥30% eGFR decline, kidney failure or kidney replacement therapy).

RESULTS

In our cohort (age 48 ± 12 years, 39% male, eGFR 63 ± 28 mL/min/1.73 m2), 59% of patients had phosphate wasting. Male sex [coefficient -0.2, 95% confidence interval (CI) -0.2; -0.1], eGFR (0.002, 95% CI 0.001; 0.004), FGF-23 (0.1, 95% CI 0.03; 0.2), PTH (-0.2, 95% CI -0.3; -0.06) and copeptin (-0.08, 95% CI -0.1; -0.08) were associated with TmP/GFR. Corrected for PTH, FGF-23 and eGFR, every 0.1 mmol/L decrease in TmP/GFR was associated with a greater eGFR decline of 0.2 mL/min/1.73 m2/year (95% CI 0.01; 0.3) and an increased hazard ratio of 1.09 (95% CI 1.01; 1.18) of the composite kidney outcome.

CONCLUSION

Our study shows that in patients with ADPKD, phosphate wasting is prevalent and associated with more rapid disease progression. Phosphate wasting may be a consequence of early proximal tubular dysfunction and insufficient suppression of PTH.

Predictors of autosomal dominant polycystic kidney disease progression: a Brazilian single-center cohort

INTRODUCTION

Identifying risk factors for autosomal dominant polycystic kidney disease (ADPKD) progression is important. However, studies that have evaluated this subject using a Brazilian sample is sparce. Therefore, the aim of this study was to identify risk factors for renal outcomes and death in a Brazilian cohort of ADPKD patients.

METHODS

Patients had the first medical appointment between January 2002 and December 2014, and were followed up until December 2019. Associations between clinical and laboratory variables with the primary outcome (sustained decrease of at least 57% in the eGFR from baseline, need for dialysis or renal transplantation) and the secondary outcome (death from any cause) were analyzed using a multiple Cox regression model. Among 80 ADPKD patients, those under 18 years, with glomerular filtration rate <30 mL/min/1.73 m2, and/or those with missing data were excluded. There were 70 patients followed.

RESULTS

The factors independently associated with the renal outcomes were total kidney length - adjusted Hazard Ratio (HR) with a 95% confidence interval (95% CI): 1.137 (1.057-1.224), glomerular filtration rate - HR (95% CI): 0.970 (0.949-0.992), and serum uric acid level - HR (95% CI): 1.643 (1.118-2.415). Diabetes mellitus - HR (95% CI): 8.115 (1.985-33.180) and glomerular filtration rate - HR (95% CI): 0.957 (0.919-0.997) were associated with the secondary outcome.

CONCLUSIONS

These findings corroborate the hypothesis that total kidney length, glomerular filtration rate and serum uric acid level may be important prognostic predictors of ADPKD in a Brazilian cohort, which could help to select patients who require closer follow up.

Data driven approach to characterize rapid decline in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic kidney disease with high phenotypic variability. Furthering insights into patients' ADPKD progression could lead to earlier detection, management, and alter the course to end stage kidney disease (ESKD). We sought to identify patients with rapid decline (RD) in kidney function and to determine clinical factors associated with RD using a data-driven approach. A retrospective cohort study was performed among patients with incident ADPKD (1/1/2002-12/31/2018). Latent class mixed models were used to identify RD patients using differences in eGFR trajectories over time. Predictors of RD were selected based on agreements among feature selection methods, including logistic, regularized, and random forest modeling. The final model was built on the selected predictors and clinically relevant covariates. Among 1,744 patients with incident ADPKD, 125 (7%) were identified as RD. Feature selection included 42 clinical measurements for adaptation with multiple imputations; mean (SD) eGFR was 85.2 (47.3) and 72.9 (34.4) in the RD and non-RD groups, respectively. Multiple imputed datasets identified variables as important features to distinguish RD and non-RD groups with the final prediction model determined as a balance between area under the curve (AUC) and clinical relevance which included 6 predictors: age, sex, hypertension, cerebrovascular disease, hemoglobin, and proteinuria. Results showed 72%-sensitivity, 70%-specificity, 70%-accuracy, and 0.77-AUC in identifying RD. 5-year ESKD rates were 38% and 7% among RD and non-RD groups, respectively. Using real-world routine clinical data among patients with incident ADPKD, we observed that six variables highly predicted RD in kidney function.

Combining genotype with height-adjusted kidney length predicts rapid progression of ADPKD

INTRODUCTION

Our main objective was to identify baseline prognostic factors predictive of rapid disease progression in a large unselected clinical autosomal dominant polycystic kidney disease (ADPKD) cohort.

METHODS

A cross-sectional analysis was performed in 618 consecutive ADPKD patients assessed and followed-up for over a decade. A total of 123 patients (19.9%) had reached kidney failure by the study date. Data were available for the following: baseline eGFR (n = 501), genotype (n = 549), baseline ultrasound mean kidney length (MKL, n = 424) and height-adjusted baseline MKL (HtMKL, n = 377). Rapid disease progression was defined as an annualized eGFR decline (∆eGFR) of >2.5 mL/min/year by linear regression over 5 years (n = 158). Patients were further divided into slow, rapid and very rapid ∆eGFR classes for analysis. Genotyped patients were classified into several categories: PKD1 (T, truncating; or NT, non-truncating), PKD2, other genes (non-PKD1 or -PKD2), no mutation detected or variants of uncertain significance.

RESULTS

A PKD1-T genotype had the strongest influence on the probability of reduced baseline kidney function by age. A multivariate logistic regression model identified PKD1-T genotype and HtMKL (>9.5 cm/m) as independent predictors for rapid disease progression. The combination of both factors increased the positive predictive value for rapid disease progression over age 40 years and of reaching kidney failure by age 60 years to 100%. Exploratory analysis in a subgroup with available total kidney volumes showed higher positive predictive value (100% vs 80%) and negative predictive value (42% vs 33%) in predicting rapid disease progression compared with the Mayo Imaging Classification (1C-E).

CONCLUSION

Real-world longitudinal data confirm the importance of genotype and kidney length as independent variables determining ∆eGFR. Individuals with the highest risk of rapid disease progression can be positively selected for treatment based on this combination.

Genomics in nephrology: identifying informatics opportunities to improve diagnosis of genetic kidney disorders using a human-centered design approach

BACKGROUND

Genomic kidney conditions often have a long lag between onset of symptoms and diagnosis. To design a real time genetic diagnosis process that meets the needs of nephrologists, we need to understand the current state, barriers, and facilitators nephrologists and other clinicians who treat kidney conditions experience, and identify areas of opportunity for improvement and innovation.

METHODS

Qualitative in-depth interviews were conducted with nephrologists and internists from 7 health systems. Rapid analysis identified themes in the interviews. These were used to develop service blueprints and process maps depicting the current state of genetic diagnosis of kidney disease.

RESULTS

Themes from the interviews included the importance of trustworthy resources, guidance on how to order tests, and clarity on what to do with results. Barriers included lack of knowledge, lack of access, and complexity surrounding the case and disease. Facilitators included good user experience, straightforward diagnoses, and support from colleagues.

DISCUSSION

The current state of diagnosis of kidney diseases with genetic etiology is suboptimal, with information gaps, complexity of genetic testing processes, and heterogeneity of disease impeding efficiency and leading to poor outcomes. This study highlights opportunities for improvement and innovation to address these barriers and empower nephrologists and other clinicians who treat kidney conditions to access and use real time genetic information.

Measured and Estimated Glomerular Filtration Rate to Evaluate Rapid Progression and Changes over Time in Autosomal Polycystic Kidney Disease: Potential Impact on Therapeutic Decision-Making

Autosomal polycystic kidney disease (ADPKD) is the most common genetic form of kidney failure, reflecting unmet needs in management. Prescription of the only approved treatment (tolvaptan) is limited to persons with rapidly progressing ADPKD. Rapid progression may be diagnosed by assessing glomerular filtration rate (GFR) decline, usually estimated (eGFR) from equations based on serum creatinine (eGFRcr) or cystatin-C (eGFRcys). We have assessed the concordance between eGFR decline and identification of rapid progression (rapid eGFR loss), and measured GFR (mGFR) declines (rapid mGFR loss) using iohexol clearance in 140 adults with ADPKD with ≥3 mGFR and eGFRcr assessments, of which 97 also had eGFRcys assessments. The agreement between mGFR and eGFR decline was poor: mean concordance correlation coefficients (CCCs) between the method declines were low (0.661, range 0.628 to 0.713), and Bland and Altman limits of agreement between eGFR and mGFR declines were wide. CCC was lower for eGFRcys. From a practical point of view, creatinine-based formulas failed to detect rapid mGFR loss (-3 mL/min/y or faster) in around 37% of the cases. Moreover, formulas falsely indicated around 40% of the cases with moderate or stable decline as rapid progressors. The reliability of formulas in detecting real mGFR decline was lower in the non-rapid-progressors group with respect to that in rapid-progressor patients. The performance of eGFRcys and eGFRcr-cys equations was even worse. In conclusion, eGFR decline may misrepresent mGFR decline in ADPKD in a significant percentage of patients, potentially misclassifying them as progressors or non-progressors and impacting decisions of initiation of tolvaptan therapy.

Estimating risk of rapid disease progression in pediatric patients with autosomal dominant polycystic kidney disease: a randomized trial of tolvaptan

BACKGROUND

Tolvaptan preserves kidney function in adults with autosomal dominant polycystic kidney disease (ADPKD) at elevated risk of rapid progression. A trial (NCT02964273) evaluated tolvaptan safety and pharmacodynamics in children (5-17 years). However, progression risk was not part of study eligibility criteria due to lack of validated criteria for risk assessment in children. As risk estimation is important to guide clinical management, baseline characteristics of the study participants were retrospectively evaluated to determine whether risk of rapid disease progression in pediatric ADPKD can be assessed and to identify parameters relevant for risk estimation.

METHODS

Four academic pediatric nephrologists reviewed baseline data and rated participant risk from 1 (lowest) to 5 (highest) based on clinical judgement and the literature. Three primary reviewers independently scored all cases, with each case reviewed by two primary reviewers. For cases with discordant ratings (≥ 2-point difference), the fourth reviewer provided a secondary rating blinded to the primary evaluations. Study participants with discordant ratings and/or for whom data were lacking were later discussed to clarify parameters relevant to risk estimation.

RESULTS

Of 90 evaluable subjects, primary reviews of 69 (77%) were concordant. The proportion considered at risk of rapid progression (final mean rating ≥ 3.5) by age group was: 15-17 years, 27/34 (79%); 12- < 15, 9/32 (28%); 4- < 12, 8/24 (33%). The panelists agreed on characteristics important for risk determination: age, kidney imaging, kidney function, blood pressure, urine protein, and genetics.

CONCLUSIONS

High ratings concordance and agreement among reviewers on relevant clinical characteristics support the feasibility of pediatric risk assessment.

How Does ADPKD Severity Differ Between Family Members?

Thousands of pathogenic variants in more than 100 genes can cause kidney cysts with substantial variability in phenotype and risk of subsequent kidney failure. Despite an established genotype-phenotype correlation in cystic kidney diseases, incomplete penetrance and variable disease expressivity are present as is the case in all monogenic diseases. In family members with autosomal dominant polycystic kidney disease (ADPKD), the same causal variant is responsible in all affected family members; however, there can still be striking discordance in phenotype severity. This narrative review explores contributors to within-family discordance in ADPKD severity. Cases of biallelic and digenic inheritance, where 2 rare pathogenic variants in cystogenic genes are coexistent in one family, account for a small proportion of within-family discordance. Genetic background, including cis and trans factors and the polygenic propensity for comorbid disease, also plays a role but has not yet been exhaustively quantified. Environmental exposures, including diet; smoking; alcohol, salt, and protein intake, and comorbid diseases, including obesity, diabetes, hypertension, kidney stones, dyslipidemia, and additional coexistent kidney diseases all contribute to ADPKD phenotypic variability among family members. Given that many of the factors contributing to phenotype variability are preventable, modifiable, or treatable, health care providers and patients need to be aware of these factors and address them in the treatment of ADPKD.

Sex, Genotype, and Liver Volume Progression as Risk of Hospitalization Determinants in Autosomal Dominant Polycystic Liver Disease

BACKGROUND & AIMS

Autosomal dominant polycystic liver disease is a rare condition with a female preponderance, based mainly on pathogenic variants in 2 genes, PRKCSH and SEC63. Clinically, autosomal dominant polycystic liver disease is characterized by vast heterogeneity, ranging from asymptomatic to highly symptomatic hepatomegaly. To date, little is known about the prediction of disease progression at early stages, hindering clinical management, genetic counseling, and the design of randomized controlled trials. To improve disease prognostication, we built a consortium of European and US centers to recruit the largest cohort of patients with PRKCSH and SEC63 liver disease.

METHODS

We analyzed an international multicenter cohort of 265 patients with autosomal dominant polycystic liver disease harboring pathogenic variants in PRKCSH or SEC63 for genotype-phenotype correlations, including normalized age-adjusted total liver volumes and polycystic liver disease-related hospitalization (liver event) as primary clinical end points.

RESULTS

Classifying individual total liver volumes into predefined progression groups yielded predictive risk discrimination for future liver events independent of sex and underlying genetic defects. In addition, disease severity, defined by age at first liver event, was considerably more pronounced in female patients and patients with PRKCSH variants than in those with SEC63 variants. A newly developed sex-gene score was effective in distinguishing mild, moderate, and severe disease, in addition to imaging-based prognostication.

CONCLUSIONS

Both imaging and clinical genetic scoring have the potential to inform patients about the risk of developing symptomatic disease throughout their lives. The combination of female sex, germline PRKCSH alteration, and rapid total liver volume progression is associated with the greatest odds of polycystic liver disease-related hospitalization.

Investigational agents for autosomal dominant polycystic kidney disease: preclinical and early phase study insights

INTRODUCTION

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inherited kidney condition caused by a single-gene mutation. It leads patients to kidney failure in more than 50% of cases by the age of 60, and, given the dominant inheritance, this disease is present in the family history in more than 90% of cases.

AREAS COVERED

This review aims to analyze the set of preclinical and early-phase studies to provide a general view of the current progress on ADPKD therapeutic options. Articles from PubMed and the current status of the trials listed in clinicaltrials.gov were examined for the review.

EXPERT OPINION

Many potential therapeutic targets are currently under study for the treatment of ADPKD. A few drugs have reached the clinical phase, while many are currently still in the preclinical phase. Organoids could be a novel approach to the study of drugs in this phase. Other than pharmacological options, very important developing approaches are represented by gene therapy and the use of MiRNA inhibitors.

The screening, diagnosis, and management of patients with autosomal dominant polycystic kidney disease: A national consensus statement from Taiwan

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited cause of end-stage kidney disease (ESKD) worldwide. Guidelines for the diagnosis and management of ADPKD in Taiwan remains unavailable. In this consensus statement, we summarize updated information on clinical features of international and domestic patients with ADPKD, followed by suggestions for optimal diagnosis and care in Taiwan. Specifically, counselling for at-risk minors and reproductive issues can be important, including ethical dilemmas surrounding prenatal diagnosis and pre-implantation genetic diagnosis. Studies reveal that ADPKD typically remains asymptomatic until the fourth decade of life, with symptoms resulting from cystic expansion with visceral compression, or rupture. The diagnosis can be made based on a detailed family history, followed by imaging studies (ultrasound, computed tomography, or magnetic resonance imaging). Genetic testing is reserved for atypical cases mostly. Common tools for prognosis prediction include total kidney volume, Mayo classification and PROPKD/genetic score. Screening and management of complications such as hypertension, proteinuria, urological infections, intracranial aneurysms, are also crucial for improving outcome. We suggest that the optimal management strategies of patients with ADPKD include general medical care, dietary recommendations and ADPKD-specific treatments. Key points include rigorous blood pressure control, dietary sodium restriction and Tolvaptan use, whereas the evidence for somatostatin analogues and mammalian target of rapamycin (mTOR) inhibitors remains limited. In summary, we outline an individualized care plan emphasizing careful monitoring of disease progression and highlight the need for shared decision-making among these patients.

Automated prognosis of renal function decline in ADPKD patients using deep learning

An accurate prognosis of renal function decline in Autosomal Dominant Polycystic Kidney Disease (ADPKD) is crucial for early intervention. Current biomarkers used are height-adjusted total kidney volume (HtTKV), estimated glomerular filtration rate (eGFR), and patient age. However, manually measuring kidney volume is time-consuming and subject to observer variability. Additionally, incorporating automatically generated features from kidney MRI images, along with conventional biomarkers, can enhance prognostic improvement. To address these issues, we developed two deep-learning algorithms. Firstly, an automated kidney volume segmentation model accurately calculates HtTKV. Secondly, we utilize segmented kidney volumes, predicted HtTKV, age, and baseline eGFR to predict chronic kidney disease (CKD) stages >=3A, >=3B, and a 30% decline in eGFR after 8 years from the baseline visit. Our approach combines a convolutional neural network (CNN) and a multi-layer perceptron (MLP). Our study included 135 subjects and the AUC scores obtained were 0.96, 0.96, and 0.95 for CKD stages >=3A, >=3B, and a 30% decline in eGFR, respectively. Furthermore, our algorithm achieved a Pearson correlation coefficient of 0.81 between predicted and measured eGFR decline. We extended our approach to predict distinct CKD stages after eight years with an AUC of 0.97. The proposed approach has the potential to enhance monitoring and facilitate prognosis in ADPKD patients, even in the early disease stages.

Validation of the Mayo Imaging Classification System for Predicting Kidney Outcomes in ADPKD

BACKGROUND

The Mayo Imaging Classification was developed to predict the rate of disease progression in patients with autosomal dominant polycystic kidney disease. This study aimed to validate its ability to predict kidney outcomes in a large multicenter autosomal dominant polycystic kidney disease cohort.

METHODS

Included were patients with ≥1 height-adjusted total kidney volume (HtTKV) measurement and ≥3 eGFR values during ≥1-year follow-up. Mayo HtTKV class stability, kidney growth rates, and eGFR decline rates were calculated. The observed eGFR decline was compared with predictions from the Mayo Clinic future eGFR equation. The future eGFR prediction equation was also tested for nonlinear eGFR decline. Kaplan-Meier survival analysis and Cox regression models were used to assess time to kidney failure using Mayo HtTKV class as a predictor variable.

RESULTS

We analyzed 618 patients with a mean age of 47±11 years and mean eGFR of 64±25 ml/min per 1.73 m 2 at baseline. Most patients (82%) remained in their baseline Mayo HtTKV class. During a mean follow-up of 5.1±2.2 years, the mean total kidney volume growth rates and eGFR decline were 5.33%±3.90%/yr and -3.31±2.53 ml/min per 1.73 m 2 per year, respectively. Kidney growth and eGFR decline showed considerable overlap between the classes. The observed annual eGFR decline was not significantly different from the predicted values for classes 1A, 1B, 1C, and 1D but significantly slower for class 1E. This was also observed in patients aged younger than 40 years and older than 60 years and those with PKD2 mutations. A polynomial model allowing nonlinear eGFR decline provided more accurate slope predictions. Ninety-seven patients (16%) developed kidney failure during follow-up. The classification predicted the development of kidney failure, although the sensitivity and positive predictive values were limited.

CONCLUSIONS

The Mayo Imaging Classification demonstrated acceptable stability and generally predicted kidney failure and eGFR decline rate. However, there was marked interindividual variability in the rate of disease progression within each class.

Exploring the impact and utility of genomic sequencing in established CKD

Clinical genetics is increasingly recognized as an important area within nephrology care. Clinicians require awareness of genetic kidney disease to recognize clinical phenotypes, consider use of genomics to aid diagnosis, and inform treatment decisions. Understanding the broad spectrum of clinical phenotypes and principles of genomic sequencing is becoming increasingly required in clinical nephrology, with nephrologists requiring education and support to achieve meaningful patient outcomes. Establishment of effective clinical resources, multi-disciplinary teams and education is important to increase application of genomics in clinical care, for the benefit of patients and their families. Novel applications of genomics in chronic kidney disease include pharmacogenomics and clinical translation of polygenic risk scores. This review explores established and emerging impacts and utility of genomics in kidney disease.

Role of Female Sex Hormones in ADPKD Progression and a Personalized Approach to Contraception and Hormonal Therapy

This review navigates the intricate relationship between gender, hormonal influences, and the progression of autosomal dominant polycystic kidney disease (ADPKD), highlighting the limited literature on this crucial topic. The study explores the impact of female sex hormones on liver and renal manifestations, uncovering gender-specific differences in disease progression. Actually, hormonal therapy in women with ADPKD remains a challenging issue and is a source of concern regarding its potential impact on disease outcomes, particularly at the hepatic level. Notably, women with ADPKD exhibit a slower renal disease progression compared to men, attributed to hormonal dynamics. This review sheds light on the role of estrogen in regulating pathways of the renin-angiotensin-aldosterone system, revealing its complex interplay and implications for cardiovascular and renal health. Therapeutic considerations for fertile women with ADPKD, including contraception options, are discussed, emphasizing the necessity for personalized approaches. In the postmenopausal phase, the review evaluates the role of hormonal replacement therapy, considering its potential benefits and risks in the context of ADPKD. The review concludes by underscoring the imperative need for tailored treatment approaches for ADPKD patients, considering individual risks and benefits. The scarcity of literature underlines the call for further research to enhance our understanding of optimal hormonal therapies in the context of ADPKD, ultimately paving the way for innovative and personalized therapeutic interventions.

Long-Term Effects of Tolvaptan in Autosomal Dominant Polycystic Kidney Disease: Predictors of Treatment Response and Safety over 6 Years of Continuous Therapy

Tolvaptan, an oral vasopressin V2 receptor antagonist, reduces renal volume expansion and loss of renal function in patients with autosomal dominant polycystic kidney disease (ADPKD). Data for predictive factors indicating patients more likely to benefit from long-term tolvaptan are lacking. Data were retrospectively collected from 55 patients on tolvaptan for 6 years. Changes in renal function, progression of renal dysfunction (estimated glomerular filtration rate [eGFR], 1-year change in eGFR [ΔeGFR/year]), and renal volume (total kidney volume [TKV], percentage 1-year change in TKV [ΔTKV%/year]) were evaluated at 3-years pre-tolvaptan, at baseline, and at 6 years. In 76.4% of patients, ΔeGFR/year improved at 6 years. The average 6-year ΔeGFR/year (range) minus baseline ΔeGFR/year: 3.024 (-8.77-20.58 mL/min/1.73 m2). The increase in TKV was reduced for the first 3 years. A higher BMI was associated with less of an improvement in ΔeGFR (p = 0.027), and family history was associated with more of an improvement in ΔeGFR (p = 0.044). Hypernatremia was generally mild; 3 patients had moderate-to-severe hyponatremia due to prolonged, excessive water intake in response to water diuresis-a side effect of tolvaptan. Family history of ADPKD and baseline BMI were contributing factors for ΔeGFR/year improvement on tolvaptan. Hyponatremia should be monitored with long-term tolvaptan administration.

The VUS Challenge in Cystic Kidney Disease: A Case-Based Review

Genetic testing in nephrology is becoming increasingly important to diagnose patients and to provide appropriate care. This is especially true for autosomal dominant polycystic kidney disease (ADPKD) because this is a common cause of kidney failure and genetically complex. In addition to the major genes, PKD1 and PKD2 , there are at least six minor loci, and phenotypic, and in some cases, genetic overlap with other cystic disorders. Targeted next-generation sequencing, a low-cost, high-throughput technique, has made routine genetic testing viable in nephrology clinics. Appropriate pre- and post-testing genetic counseling is essential to the testing process. Carefully assessing variants is also critical, with the genetic report classifying variants in accordance with American College of Medical Genetics and Genomics guidelines. However, variant of uncertain significance (VUSs) may pose a significant challenge for the ordering clinician. In ADPKD, and particularly within PKD1 , there is high allelic heterogeneity; no single variant is present in more than 2% of families. The Mayo/Polycystic Kidney Disease Foundation variant database, a research tool, is the best current database of PKD1 and PKD2 variants containing over 2300 variants identified in individuals with polycystic kidney disease, but novel variants are often identified. In patients with a high pretest probability of ADPKD on the basis of clinical criteria, but no finding of a pathogenic (P) or likely pathogenic (LP) variant in a cystic kidney gene, additional evaluation of cystic gene VUS can be helpful. In this case-based review, we propose an algorithm for the assessment of such variants in a clinical setting and show how some can be reassigned to a diagnostic grouping. When assessing the relevance of a VUS, we consider both patient/family-specific and allele-related factors using population and variant databases and available prediction tools, as well as genetic expertise. This analysis plus further family studies can aid in making a genetic diagnosis.

DKK3 as a potential novel biomarker in patients with autosomal polycystic kidney disease

Backgound

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease, and leads to a steady loss of kidney function in adulthood. The variable course of the disease makes it necessary to identify the patients with rapid disease progression who will benefit the most from targeted therapies and interventions. Currently, magnetic resonance imaging-based volumetry of the kidney is the most commonly used tool for this purpose. Biomarkers that can be easily and quantitatively determined, which allow a prediction of the loss of kidney function, have not yet been established in clinical practice. The glycoprotein Dickkopf 3 (DKK3) which is secreted in the renal tubular epithelium upon stress and contributes to tubulointerstitial fibrosis via the Wnt signaling pathway, was recently described as a biomarker for estimating risk of kidney function loss, but has not been investigated for ADPKD. This study aimed to obtain a first insight into whether DKK3 may indeed improve outcome prediction in ADPKD in the future.

Methods

In 184 ADPKD patients from the AD(H)PKD registry and 47 healthy controls, the urinary DKK3 (uDKK3) levels were determined using ELISA. Multiple linear regression was used to examine the potential of these values in outcome prediction.

Results

ADPKD patients showed significantly higher uDKK3 values compared with the controls (mean 1970 ± 5287 vs 112 ± 134.7 pg/mg creatinine). Furthermore, there was a steady increase in uDKK3 with an increase in the Mayo class (A/B 1262 ± 2315 vs class D/E 3104 ± 7627 pg/mg creatinine), the best-established biomarker of progression in ADPKD. uDKK3 also correlated with estimated glomerular filtration rate (eGFR). Patients with PKD1 mutations show higher uDKK3 levels compared with PKD2 patients (PKD1: 2304 ± 5119; PKD2: 506.6 ± 526.8 pg/mg creatinine). Univariate linear regression showed uDKK3 as a significant predictor of future eGFR slope estimation. In multiple linear regression this effect was not significant in models also containing height-adjusted total kidney volume and/or eGFR. However, adding both copeptin levels and the interaction term between copeptin and uDKK3 to the model resulted in a significant predictive value of all these three variables and the highest R2 of all models examined (∼0.5).

Conclusion

uDKK3 shows a clear correlation with the Mayo classification in patients with ADPKD. uDKK3 levels correlated with kidney function, which could indicate that uDKK3 also predicts a disproportionate loss of renal function in this collective. Interestingly, we found an interaction between copeptin and uDKK3 in our prediction models and the best model containing both variables and their interaction term resulted in a fairly good explanation of variance in eGFR slope compared with previous models. Considering the limited number of patients in these analyses, future studies will be required to confirm the results. Nonetheless, uDKK3 appears to be an attractive candidate to improve outcome prediction of ADPKD in the future.

DNAJB11 Mutation in ADPKD Patients: Clinical Characteristics in a Monocentric Cohort

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a late-onset cilia-related disorder, characterized by progressive cystic enlargement of the kidneys. It is genetically heterogeneous with PKD1 and PKD2 pathogenic variants identified in approximately 78% and 15% of families, respectively. More recently, additional ADPKD genes, such as DNAJB11, have been identified and included in the diagnostic routine test for renal cystic diseases. However, despite recent progress in ADPKD molecular approach, approximately ~7% of ADPKD-affected families remain genetically unresolved. We collected a cohort of 4 families from our center, harboring heterozygous variants in the DNAJB11 gene along with clinical and imaging findings consistent with previously reported features in DNAJB11 mutated patients. Mutations were identified as likely pathogenetic (LP) in three families and as variants of uncertain significance (VUS) in the remaining one. One patient underwent to kidney biopsy and showed a prevalence of interstitial fibrosis that could be observed in ~60% of the sample. The presence in the four families from our cohort of ADPKD characteristics together with ADTKD features, such as hyperuricemia, diabetes, and chronic interstitial fibrosis, supports the definition of DNAJB11 phenotype as an overlap disease between these two entities, as originally suggested by the literature.

Beyond Loss of Kidney Function: Patient Care in Autosomal Dominant Polycystic Kidney Disease

Patients with autosomal dominant polycystic kidney disease benefit from specialized care over their lifetimes, starting with diagnosis of the condition with ongoing discussion of both the renal course and extra-renal issues. Both renal and extra-renal issues may continue to cause major morbidity even after successful kidney transplant or initiation of RRT, and extra-renal disease aspects should always be considered as part of routine management. In this review, we will focus on updates in pain/depression screening, cardiac manifestations, liver and pancreatic cysts, kidney stone management, and genetic counseling. In some instances, we have shared our current clinical practice rather than an evidence-based guideline. We anticipate more standardization of care after the release of the Kidney Disease Improving Global Outcomes guidelines for management in autosomal dominant polycystic kidney disease later this year.

Feasibility and impact of ketogenic dietary interventions in polycystic kidney disease: KETO-ADPKD-a randomized controlled trial

Ketogenic dietary interventions (KDIs) are beneficial in animal models of autosomal-dominant polycystic kidney disease (ADPKD). KETO-ADPKD, an exploratory, randomized, controlled trial, is intended to provide clinical translation of these findings (NCT04680780). Sixty-six patients were randomized to a KDI arm (ketogenic diet [KD] or water fasting [WF]) or the control group. Both interventions induce significant ketogenesis on the basis of blood and breath acetone measurements. Ninety-five percent (KD) and 85% (WF) report the diet as feasible. KD leads to significant reductions in body fat and liver volume. Additionally, KD is associated with reduced kidney volume (not reaching statistical significance). Interestingly, the KD group exhibits improved kidney function at the end of treatment, while the control and WF groups show a progressive decline, as is typical in ADPKD. Safety-relevant events are largely mild, expected (initial flu-like symptoms associated with KD), and transient. Safety assessment is complemented by nuclear magnetic resonance (NMR) lipid profile analyses.

Predicting autosomal dominant polycystic kidney disease progression: review of promising Serum and urine biomarkers

Autosomal dominant polycystic kidney disease (ADPKD) is one of the leading causes of end-stage renal disease. In spite of the recent tremendous progress in the understanding of ADPKD pathogenesis, the molecular mechanisms of the disease remain incompletely understood. Considering emerging new targeted therapies for ADPKD, it has become crucial to disclose easily measurable and widely available biomarkers for identifying patients with future rapid disease progression. This review encompasses all the research with a shared goal of identifying promising serum or urine biomarkers for predicting ADPKD progression or response to therapy. The rate of the ADPKD progress varies significantly between patients. The phenotypic variability is only partly explained by the underlying genetic lesion diversity. Considering significant decline in kidney function in ADPKD is not usually evident until at least 50% of the parenchyma has been destroyed, conventional kidney function measures, such as glomerular filtration rate (GFR), are not suitable for monitoring disease progression in ADPKD, particularly in its early stages. Since polycystic kidney enlargement usually precedes the decline in GFR, height-adjusted total kidney volume (ht-TKV) has been accepted as an early biomarker for assessing disease severity in ADPKD patients. However, since measuring ht-TKV is time-consuming and observer-dependent, the identification of a sensitive and quickly measurable biomarker is of a great interest for everyday clinical practice. Throughout the last decade, due to development of proteomic and metabolomic techniques and the enlightenment of multiple molecular pathways involved in the ADPKD pathogenesis, a number of urine and serum protein biomarkers have been investigated in ADPKD patients, some of which seem worth of further exploring. These include copeptin, angiotensinogen, monocyte chemoattractant protein 1, kidney injury molecule-1 and urine-to-plasma urea ratio among many others. The aim of the current review is to provide an overview of all of the published evidence on potentially clinically valuable serum and urine biomarkers that could be used for predicting disease progression or response to therapy in patients with ADPKD. Hopefully, this review will encourage future longitudinal prospective clinical studies evaluating proposed biomarkers as prognostic tools to improve management and outcome of ADPKD patients in everyday clinical practice.

Cardiometabolic comorbidities in autosomal dominant polycystic kidney disease: a 16-year retrospective cohort study

BACKGROUND

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent hereditary kidney disease and the fourth leading cause of end-stage renal disease (ESRD) requiring renal replacement therapy (RRT). Nevertheless, there is a paucity of epidemiological research examining the risk factors and survival on RRT for ADPKD. Thus, we aimed to investigate the cumulative effects of cardiometabolic comorbidities, including hypertension (HTN), type 2 diabetes mellitus (DM), and dyslipidemia (DLP) to clinical outcomes in ADPKD.

METHODS

We identified 6,142 patients with ADPKD aged ≥ 20 years from 2000 to 2015 using a nationwide population-based database. HTN, DM, and DLP diagnoses before or at the time of ADPKD diagnosis and different combinations of the three diagnoses were used as the predictors for the outcomes. Survival analyses were used to estimate the adjusted mortality risk from cardiometabolic comorbidities and the risk for renal survival.

RESULTS

Patients with ADPKD who developed ESRD had the higher all-cause mortality (HR, 5.14; [95% CI: 3.88-6.80]). Patients with all three of the diseases had a significantly higher risk of entering ESRD (HR:4.15, [95% CI:3.27-5.27]), followed by those with HTN and DM (HR:3.62, [95% CI:2.82-4.65]), HTN and DLP (HR:3.54, [95% CI:2.91-4.31]), and HTN alone (HR:3.10, [95% CI:2.62-3.66]) compared with those without any three cardiometabolic comorbidities.

CONCLUSIONS

Our study discovered the cumulative effect of HTN, DM, and DLP on the risk of developing ESRD, which reinforces the urgency of proactive prevention of cardiometabolic comorbidities to improve renal outcomes and overall survival in ADPKD patients.

Case report: Genotype-phenotype characteristics of nine novel PKD1 mutations in eight Chinese patients with autosomal dominant polycystic kidney disease

Introduction

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder. The PKD1 gene is responsible for the majority of ADPKD cases, and the mutations in this gene exhibit high genetic diversity. This study aimed to investigate the association between genotype and phenotype in ADPKD patients with PKD1 gene mutations through pedigree analysis.

Methods

Eight Chinese pedigrees affected by ADPKD were analyzed using whole-exome sequencing (WES) on peripheral blood DNA. The identified variants were validated using Sanger sequencing, and clinical data from the patients and their families were collected and analyzed.

Results

Nine novel mutation sites in PKD1 were discovered across the pedigrees, including c.4247T > G, c.3298_3301delGAGT, c.4798A > G, c.7567G > A, c.11717G > C, c.7703 + 5G > C, c.3296G > A, c.8515_8516insG, and c.5524C > A. These mutations were found to be associated with a range of clinical phenotypes, including chronic kidney disease, hypertension, and polycystic liver. The age of onset and disease progression displayed significant heterogeneity among the pedigrees, with some individuals exhibiting early onset and rapid disease progression, while others remained asymptomatic or had milder disease symptoms. Inheritance patterns supported autosomal dominant inheritance, as affected individuals inherited the mutations from affected parents. However, there were instances of individuals carrying the mutations who remained asymptomatic or exhibited milder disease phenotypes.

Conclusion

This study highlights the importance of comprehensive genotype analysis in understanding the progression and prognosis of ADPKD. The identification of novel mutation sites expands our knowledge of PKD1 gene mutations. These findings contribute to a better understanding of the disease and may have implications for personalized therapeutic strategies.

Subclinical Target Organ Damage in a Sample of Children with Autosomal Dominant Polycystic Kidney Disease: A Pilot Study

Background and Objectives: Hypertension and vascular damage can begin in adolescents affected by Autosomal Dominant Polycystic Kidney Disease (ADPKD). This study aimed to evaluate markers of vascular damage and left ventricular geometry in a sample of children with ADPKD. Materials and Methods: Several vascular measurements were obtained: ambulatory blood pressure monitoring (ABPM), carotid intima-media thickness (cIMT), carotid distensibility coefficient (cDC), pulse wave velocity (PWV), and echocardiographic measurements (relative wall thickness (RWT) and left ventricular mass index (LVMI)). Results: Eleven ADPKD children were recruited (four females and seven males, mean age 9.5 ± 3.2 years). Four children were hypertensive at the ABPM, five were normotensive, and for two ABPM was not available. RWT was tendentially high (mean 0.47 ± 0.39). Eight patients had concentric cardiac remodeling, while one patient had cardiac hypertrophy. cIMT was above the 95° percentile for sex and height in 80% of the children (0.5 ± 0.005 mm). The average PWV and cDC were between the normal range (5.5 ± 4.6 m/s and 89.6 ± 16.1 × 10-3/KPa, respectively). We observed a positive correlation between the PWV and RWT (r = 0.616; p = 0.044) and a negative correlation between cDC and RWT (r = -0.770; p = 0.015). Cardiovascular damages (cIMT > 95° percentile) were found in normotensive patients. Conclusions: Increased RWT and high cIMT, indicating subclinical organ damage, are already present in ADPKD children. RWT was significantly correlated to that of cDC and PWV, implying that vascular stiffening is associated with cardiac remodeling. None of the children had an alteration in renal function. Subclinical cardiovascular damage preceded the decline in glomerular filtration rate.

Short-Term Dapagliflozin Administration in Autosomal Dominant Polycystic Kidney Disease-A Retrospective Single-Arm Case Series Study

Treatment with sodium-glucose cotransporter-2 (SGLT2) inhibitors may have pleiotropic and beneficial effects in terms of ameliorating of risk factors for the progression of autosomal dominant polycystic kidney disease (ADPKD). However, there is insufficient evidence regarding the use of these drugs in patients with ADPKD, as they were excluded from several clinical trials conducted to explore kidney protection provided by SGLT2 inhibitors. This retrospective single-arm case series study was performed to investigate the effects of dapagliflozin, a selective SGLT2 inhibitor administered at 10 mg/day, on changes in height-adjusted kidney volume (htTKV) and estimated glomerular filtration rate (eGFR) in ADPKD patients. During a period of 102 ± 20 days (range 70-156 days), eGFR was decreased from 47.9 (39.7-56.9) to 40.8 (33.7-44.5) mL/min/1.73 m2 (p < 0.001), while htTKV was increased from 599 (423-707) to 617 (446-827) mL/m (p = 0.002) (n = 20). The annual increase in htTKV rate was significantly promoted, and urinary phosphate change was found to be correlated with the change in htTKV (rs = 0.575, p = 0.020). In the examined patients, eGFR was decreased and htTKV increased during short-term administration of dapagliflozin. To confirm the possibility of the effects of dapagliflozin on ADPKD, additional interventional studies are required.

Development and Validation of a Nomogram for Renal Survival Prediction in Patients with Autosomal Dominant Polycystic Kidney Disease

Introduction

Due to the wide variation in the prognosis of autosomal dominant polycystic kidney disease (ADPKD), prediction of risk of renal survival in ADPKD patients is a tough challenge. We aimed to establish a nomogram for the prediction of renal survival in ADPKD patients.

Methods

We conducted a retrospective observational cohort study in 263 patients with ADPKD. The patients were randomly assigned to a training set (N = 198) and a validation set (N = 65), and demographic and statistical data at baseline were collected. The total kidney volume was measured using stereology. A clinical prediction nomogram was developed based on multivariate Cox regression results. The performance and clinical utility of the nomogram were assessed by calibration curves, the concordance index (C-index), and decision curve analysis (DCA). The nomogram was compared with the height-adjusted total kidney volume (htTKV) model by receiver operating characteristic curve analysis and DCA.

Results

The five independent factors used to construct the nomogram for prognosis prediction were age, htTKV, estimated glomerular filtration rate, hypertension, and hemoglobin. The calibration curve of predicted probabilities against observed renal survival indicated excellent concordance. The model showed very good discrimination with a C-index of 0.91 (0.83-0.99) and an area under the curve of 0.94, which were significantly higher than those of the htTKV model. Similarly, DCA demonstrated that the nomogram had a better net benefit than the htTKV model.

Conclusion

The risk prediction nomogram, incorporating easily assessable clinical parameters, was effective for the prediction of renal survival in ADPKD patients. It can be a useful clinical adjunct for clinicians to evaluate the prognosis of ADPKD patients and provide individualized decision-making.

A long-read sequencing and SNP haplotype-based novel preimplantation genetic testing method for female ADPKD patient with de novo PKD1 mutation

The autosomal dominant form of polycystic kidney disease (ADPKD) is the most common hereditary disease that causes late-onset renal cyst development and end-stage renal disease. Preimplantation genetic testing for monogenic disease (PGT-M) has emerged as an effective strategy to prevent pathogenic mutation transmission rely on SNP linkage analysis between pedigree members. Yet, it remains challenging to establish reliable PGT-M methods for ADPKD cases or other monogenic diseases with de novo mutations or without a family history. Here we reported the application of long-read sequencing for direct haplotyping in a female patient with de novo PKD1 c.11,526 G > C mutation and successfully established the high-risk haplotype. Together with targeted short-read sequencing of SNPs for the couple and embryos, the carrier status for embryos was identified. A healthy baby was born without the PKD1 pathogenic mutation. Our PGT-M strategy based on long-read sequencing for direct haplotyping combined with targeted SNP haplotype can be widely applied to other monogenic disease carriers with de novo mutation.

Genetic Spectrum of Polycystic Kidney and Liver Diseases and the Resulting Phenotypes

Polycystic kidney diseases are a group of monogenically inherited disorders characterized by cyst development in the kidney with defects in primary cilia function central to pathogenesis. Autosomal dominant polycystic kidney disease (ADPKD) has progressive cystogenesis and accounts for 5-10% of kidney failure (KF) patients. There are two major ADPKD genes, PKD1 and PKD2, and seven minor loci. PKD1 accounts for ∼80% of patients and is associated with the most severe disease (KF is typically at 55-65 years); PKD2 accounts for ∼15% of families, with KF typically in the mid-70s. The minor genes are generally associated with milder kidney disease, but for DNAJB11 and ALG5, the age at KF is similar to PKD2. PKD1 and PKD2 have a high level of allelic heterogeneity, with no single pathogenic variant accounting for >2% of patients. Additional genetic complexity includes biallelic disease, sometimes causing very early-onset ADPKD, and mosaicism. Autosomal dominant polycystic liver disease is characterized by severe PLD but limited PKD. The two major genes are PRKCSH and SEC63, while GANAB, ALG8, and PKHD1 can present as ADPKD or autosomal dominant polycystic liver disease. Autosomal recessive polycystic kidney disease typically has an infantile onset, with PKHD1 being the major locus and DZIP1L and CYS1 being minor genes. In addition, there are a range of mainly recessive syndromic ciliopathies with PKD as part of the phenotype. Because of the phenotypic and genic overlap between the diseases, employing a next-generation sequencing panel containing all known PKD and ciliopathy genes is recommended for clinical testing.

Assessing the Risk of Progression to Kidney Failure in Patients With Autosomal Dominant Polycystic Kidney Disease

While autosomal dominant polycystic kidney disease (ADPKD) is a dichotomous diagnosis, substantial variability in disease severity exists. Identification of inherited risk through family history, genetic testing, and environmental risk factors through clinical assessment are important components of risk assessment for optimal management of patients with ADPKD. Genetic testing is especially helpful in cases with diagnostic uncertainty, particularly in cases with no apparent family history, in young cases (age less than 25 years) where a definitive diagnosis is sought, or in atypical presentations with early, severe, or discordant findings. Currently, risk assessment in ADPKD may be performed with the use of age-adjusted estimated glomerular filtration rate thresholds, evidence of rapid estimated glomerular filtration rate decline on serial measurements, age- and height-adjusted total kidney volume by Mayo Clinic Imaging Classification, or evidence of early hypertension and urological complications combined with PKD1 or PKD2 mutation class; however, caveats exist with each of these approaches. Fine-tuning of risk stratification with advanced imaging features and biomarkers is the subject of research but is not yet ready for general clinical practice. While conservative treatment strategies will be advised for all patients, those with the greatest rate of disease progression will have the most benefit from aggressive disease-modifying therapy. In this narrative review, we will summarize the evidence behind the clinical assessment and risk stratification of patients with ADPKD.

Clinical Characteristics of Rapid Progression in Asia-Pacific Patients With ADPKD

Introduction

This study aimed to determine the utility of different methods to predict rapid progressors (RPs) and their clinical characteristics in Asia-Pacific patients with autosomal dominant polycystic kidney disease (ADPKD).

Methods

This was a multinational retrospective observational cohort study of patients with ADPKD in the Asia-Pacific region. Five hospitals from Australia, China, South Korea, Taiwan, and Turkey participated in this study. RP was defined by European Renal Association-European Dialysis and Transplantation Association (ERA-EDTA) guidelines and compared to slow progressors (SPs).

Results

Among 768 patients, 426 patients were RPs. Three hundred six patients met only 1 criterion and 120 patients satisfied multiple criteria for RP. Historical estimated glomerular filtration rate (eGFR) decline fulfilled the criteria for RP in 210 patients. Five patients met the criteria for a historical increase in height-adjusted total kidney volume (TKV). The 210 patients satisfied the criteria for based on kidney volume. During the follow-up period, cyst infections, cyst hemorrhage, and proteinuria occurred more frequently in RP; and 13.9% and 2.1% of RPs and SPs, respectively, progressed to end-stage kidney disease (ESKD). RP criteria based on historical eGFR decline had the strongest correlation with eGFR change over a 2-year follow-up.

Conclusion

Various assessment strategies should be used for identifying RPs among Asian-Pacific patients with ADPKD in real-world clinical practice during the follow-up period, cyst infections, cyst hemorrhage, and proteinuria occurred more frequently; and more patients progressed to ESKD in RPs compared with SPs.