Type of PKD1 mutation influences renal outcome in ADPKD

MicroRNA and renal fibrosis in autosomal dominant polycystic kidney disease: a longitudinal study

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary kidney disorder that may progress to kidney failure, accounting for 5-10% of all patients with end-stage kidney disease (ESKD). Clinical data, as well as molecular genetics and advanced imaging techniques have provided surrogate prognostic biomarkers to predict rapid decline in kidney function, nonetheless enhanced tools for assessing prognosis for ADPKD are still needed. The aim of this study was to analyze specific microRNAs involved in the pathogenesis of ADPKD and in the development of renal fibrosis, evaluating their potential role as predictors of renal function loss.

METHODS

We evaluated kidney function by estimated glomerular filtration rate (eGFR) in 32 ADPKD patients in different stages of kidney disease at T0 and after a 24-month follow up (T1). Patients were divided into two groups: Rapid disease progression ([RP], n 15) and Non-rapid disease progression ([NRP], n 17), according to the Mayo Clinic classification criteria. At T0, ADPKD patients underwent plasma sampling for quantitative analysis of h-miR-17-5p, h-miR-21-5p and h-miR-199a-5p microRNA expression, using the quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) method and a 3 T magnetic resonance imaging (MRI), using an advanced MRI imaging protocol, for the quantification of total kidney volume (TKV), total perfusion volume (TPV) and total fibrotic volume (TFV).

RESULTS

The expression of h-miR17-5p was higher (p < 0.05) in ADPKD patients with rapid disease progression. h-miR-17-5p, h-miR-21-5p and h-mir-199-5p showed a positive and significant correlation with the eGFR slope (mL/min/1.73 m2/year) (p < 0.05) but not with the eGFR at both T0 and T1. Both total fibrotic volume (cm3) and height-adjusted total fibrotic volume (cm3/m) were positively and significantly correlated to h-miR 21-5p and h-miR 199-5p (p < 0.05), but not to total kidney volume (cm3) and height-adjusted total kidney volume (cm3/m).

CONCLUSIONS

The microRNAs we studied were associated with fibrosis and renal damage, suggesting their possible role as biomarkers able to identify ADPKD patients at high risk of disease progression regardless of the degree of kidney function, and therefore suitable for medical therapy, and may help uncovering new molecular mechanisms underlying cystogenesis.

Reprogramming of Energy Metabolism in Human PKD1 Polycystic Kidney Disease: A Systems Biology Analysis

Multiple alterations of cellular metabolism have been documented in experimental studies of autosomal dominant polycystic kidney disease (ADPKD) and are thought to contribute to its pathogenesis. To elucidate the molecular pathways and transcriptional regulators associated with the metabolic changes of renal cysts in ADPKD, we compared global gene expression data from human PKD1 renal cysts, minimally cystic tissues (MCT) from the same patients, and healthy human kidney cortical tissue samples. We found gene expression profiles of PKD1 renal cysts were consistent with the Warburg effect with gene pathway changes favoring increased cellular glucose uptake and lactate production, instead of pyruvate oxidation. Additionally, mitochondrial energy metabolism was globally depressed, associated with downregulation of gene pathways related to fatty acid oxidation (FAO), branched-chain amino acid (BCAA) degradation, the Krebs cycle, and oxidative phosphorylation (OXPHOS) in renal cysts. Activation of mTORC1 and its two target proto-oncogenes, HIF-1α and MYC, was predicted to drive the expression of multiple genes involved in the observed metabolic reprogramming (e.g., GLUT3, HK1/HK2, ALDOA, ENO2, PKM, LDHA/LDHB, MCT4, PDHA1, PDK1/3, MPC1/2, CPT2, BCAT1, NAMPT); indeed, their predicted expression patterns were confirmed by our data. Conversely, we found AMPK inhibition was predicted in renal cysts. AMPK inhibition was associated with decreased expression of PGC-1α, a transcriptional coactivator for transcription factors PPARα, ERRα, and ERRγ, all of which play a critical role in regulating oxidative metabolism and mitochondrial biogenesis. These data provide a comprehensive map of metabolic pathway reprogramming in ADPKD and highlight nodes of regulation that may serve as targets for therapeutic intervention.

Increased Expression of Orexin-A in Patients Affected by Polycystic Kidney Disease

Orexin-A is a neuropeptide product of the lateral hypothalamus that acts on two receptors, OX1R and OX2R. The orexinergic system is involved in feeding, sleep, and pressure regulation. Recently, orexin-A levels have been found to be negatively correlated with renal function. Here, we analyzed orexin-A levels as well as the incidence of SNPs in the hypocretin neuropeptide precursor (HCRT) and its receptors, HCRTR1 and HCRTR2, in 64 patients affected by autosomal dominant polycystic kidney disease (ADPKD) bearing truncating mutations in the PKD1 or PKD2 genes. Twenty-four healthy volunteers constituted the control group. Serum orexin-A was assessed by ELISA, while the SNPs were investigated through Sanger sequencing. Correlations with the main clinical features of PKD patients were assessed. PKD patients showed impaired renal function (mean eGFR 67.8 ± 34.53) and a statistically higher systolic blood pressure compared with the control group (p < 0.001). Additionally, orexin-A levels in PKD patients were statistically higher than those in healthy controls (477.07 ± 69.42 pg/mL vs. 321.49 ± 78.01 pg/mL; p < 0.001). Furthermore, orexin-A inversely correlated with blood pressure (p = 0.0085), while a direct correlation with eGFR in PKD patients was found. None of the analyzed SNPs showed any association with orexin-A levels in PKD. In conclusion, our data highlights the emerging role of orexin-A in renal physiology and its potential relevance to PKD. Further research is essential to elucidate the intricate mechanisms underlying orexin-A signaling in renal function and its therapeutic implications for PKD and associated cardiovascular complications.

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.

Comprehensive Analysis of PKD1 and PKD2 by Long-Read Sequencing in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by heterogeneous variants in the PKD1 and PKD2 genes. Genetic analysis of PKD1 has been challenging due to homology with 6 PKD1 pseudogenes and high GC content.

METHODS

A single-tube multiplex long-range-PCR and long-read sequencing-based assay termed "comprehensive analysis of ADPKD" (CAPKD) was developed and evaluated in 170 unrelated patients by comparing to control methods including next-generation sequencing (NGS) and multiplex ligation-dependent probe amplification.

RESULTS

CAPKD achieved highly specific analysis of PKD1 with a residual noise ratio of 0.05% for the 6 pseudogenes combined. CAPKD identified PKD1 and PKD2 variants (ranging from variants of uncertain significance to pathogenic) in 160 out of the 170 patients, including 151 single-nucleotide variants (SNVs) and insertion-deletion variants (indels), 6 large deletions, and one large duplication. Compared to NGS, CAPKD additionally identified 2 PKD1 variants (c.78_96dup and c.10729_10732dup). Overall, CAPKD increased the rate of variant detection from 92.9% (158/170) to 94.1% (160/170), and the rate of diagnosis with pathogenic or likely pathogenic variants from 82.4% (140/170) to 83.5% (142/170). CAPKD also directly determined the cis-/trans-configurations in 11 samples with 2 or 3 SNVs/indels, and the breakpoints of 6 large deletions and one large duplication, including 2 breakpoints in the intron 21 AG-repeat of PKD1, which could only be correctly characterized by aligning to T2T-CHM13.

CONCLUSIONS

CAPKD represents a comprehensive and specific assay toward full characterization of PKD1 and PKD2 variants, and improves the genetic diagnosis for ADPKD.

Genotype-phenotype of autosomal dominant polycystic kidney disease in Malta

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the development of multiple renal cysts causing kidney enlargement and end-stage renal disease (ESRD) in half the patients by 60 years of age. The aim of the study was to determine the genetic aetiology in Maltese patients clinically diagnosed with ADPKD and correlate the clinical features.

METHODS

A total of 60 patients over 18 years of age clinically diagnosed with ADPKD were studied using a customized panel of genes that had sufficient evidence of disease diagnosis using next generation sequencing (NGS). The genes studied were PKD1, PKD2, GANAB, DNAJB11, PKHD1 and DZIP1L. Selected variants were confirmed by bidirectional Sanger sequencing with specifically designed primers. Cases where no clinically significant variant was identified by the customized gene panel were then studied by Whole Exome Sequencing (WES). Microsatellite analysis was performed to determine the origin of an identified recurrent variant in the PKD2 gene. Clinical features were studied for statistical correlation with genetic results.

RESULTS

Genetic diagnosis was reached in 49 (82%) of cases studied. Pathogenic/likely pathogenic variants PKD1 and PKD2 gene were found in 25 and in 23 cases respectively. The relative proportion of genetically diagnosed PKD1:PKD2 cases was 42:38. A pathogenic variant in the GANAB gene was identified in 1 (2%) case. A potentially significant heterozygous likely pathogenic variant was identified in PKHD1 in 1 (2%) case. Potentially significant variants of uncertain significance were seen in 4 (7%) cases of the study cohort. No variants in DNAJB11 and DZIP1L were observed. Whole exome sequencing (WES) added the diagnostic yield by 10% over the gene panel analysis. Overall no clinically significant variant was detected in 6 (10%) cases of the study population by a customized gene panel and WES. One recurrent variant the PKD2 c.709+1G > A was observed in 19 (32%) cases. Microsatellite analysis showed that all variant cases shared the same haplotype indicating that their families may have originated from a common ancestor and confirmed it to be a founder variant in the Maltese population. The rate of decline in eGFR was steeper and progression to ESRD was earlier in cases with PKD1 variants when compared to cases with PKD2 variants. Cases segregating truncating variants in PKD1 showed a significantly earlier onset of ESRD and this was significantly worse in cases with frameshift variants. Overall extrarenal manifestations were commoner in cases segregating truncating variants in PKD1.

CONCLUSIONS

This study helps to show that a customized gene panel is the first-line method of choice for studying patients with ADPKD followed by WES which increased the detection of variants present in the PKD1 pseudogene region. A founder variant in the PKD2 gene was identified in our Maltese cohort with ADPKD. Phenotype of patients with ADPKD is significantly related to the genotype confirming the important role of molecular investigations in the diagnosis and prognosis of polycystic kidney disease. Moreover, the findings also highlight the variability in the clinical phenotype and indicate that other factors including epigenetic and environmental maybe be important determinants in Autosomal Dominant Polycystic Kidney Disease.

Protocol for the nationwide registry of patients with polycystic kidney disease: japanese national registry of PKD (JRP)

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are major genetic polycystic kidney diseases that can progress to end-stage kidney disease (ESKD). Longitudinal data on the clinical characteristics associated with clinical outcomes in polycystic kidney disease (PKD), including the development of ESKD and cardiovascular disease (CVD) are lacking in Japan. To address this unmet need the authors are establishing a novel, web-based, Nationwide Cohort Registry Study-the Japanese Registry of PKD (JRP).

METHODS

The JRP is a prospective cohort study for ADPKD (aim to recruit n = 1000 patients), and both a retrospective and prospective study for ARPKD (aim to recruit n = 100). In the prospective registry, patients will be followed-up for 10 years every 6 months and 12 months for patients with ADPKD and ARPKD, respectively. Data collection will be recorded on Research Electronic Data Capture (REDCap) starting on April 1, 2024, with recruitment ending on March 31, 2029. (jRCT 1030230618).

RESULTS

Data to be collected include: baseline data, demographics, diagnostic and genetic information, radiological and laboratory findings, and therapeutic interventions. During follow-up, clinical events such as development of ESKD, hospitalization, occurrence of extra kidney complications including CVD events, and death will be recorded, as well as patient-reported health-related quality of life for patients with ADPKD.

CONCLUSIONS

The JRP is the first nationwide registry study for patients with ADPKD and ARPKD in Japan, providing researchers with opportunities to advance knowledge and treatments for ADPKD and ARPKD, and to inform disease management and future clinical practice.

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.

Glis2 is an early effector of polycystin signaling and a target for therapy in polycystic kidney disease

Mouse models of autosomal dominant polycystic kidney disease (ADPKD) show that intact primary cilia are required for cyst growth following the inactivation of polycystin-1. The signaling pathways underlying this process, termed cilia-dependent cyst activation (CDCA), remain unknown. Using translating ribosome affinity purification RNASeq on mouse kidneys with polycystin-1 and cilia inactivation before cyst formation, we identify the differential 'CDCA pattern' translatome specifically dysregulated in kidney tubule cells destined to form cysts. From this, Glis2 emerges as a candidate functional effector of polycystin signaling and CDCA. In vitro changes in Glis2 expression mirror the polycystin- and cilia-dependent changes observed in kidney tissue, validating Glis2 as a cell culture-based indicator of polycystin function related to cyst formation. Inactivation of Glis2 suppresses polycystic kidney disease in mouse models of ADPKD, and pharmacological targeting of Glis2 with antisense oligonucleotides slows disease progression. Glis2 transcript and protein is a functional target of CDCA and a potential therapeutic target for treating ADPKD.

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.

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.

Genetics of cystogenesis in base-edited human organoids reveal therapeutic strategies for polycystic kidney disease

In polycystic kidney disease (PKD), microscopic tubules expand into macroscopic cysts. Among the world's most common genetic disorders, PKD is inherited via heterozygous loss-of-function mutations but is theorized to require additional loss of function. To test this, we establish human pluripotent stem cells in allelic series representing four common nonsense mutations, using CRISPR base editing. When differentiated into kidney organoids, homozygous mutants spontaneously form cysts, whereas heterozygous mutants (original or base corrected) express no phenotype. Using these, we identify eukaryotic ribosomal selective glycosides (ERSGs) as PKD therapeutics enabling ribosomal readthrough of these same nonsense mutations. Two different ERSGs not only prevent cyst initiation but also limit growth of pre-formed cysts by partially restoring polycystin expression. Furthermore, glycosides accumulate in cyst epithelia in organoids and mice. Our findings define the human polycystin threshold as a surmountable drug target for pharmacological or gene therapy interventions, with relevance for understanding disease mechanisms and future clinical trials.

US Veterans Administration Autosomal Dominant Polycystic Kidney Disease Cohort: Demographic, Comorbidity, and Key Laboratory Data Characteristics

Key Points

We built a cohort of 12,217 patients diagnosed with autosomal dominant polycystic kidney disease from 1999 to 2020 in the national Veteran Affairs electronic medical record system. We characterized the cohort on demographics, comorbidities, and key laboratory measurements.

Background

We used the largest integrated US healthcare system, the Veterans Health Administration, to establish a robust resource for demographic, longitudinal outcome, and predictive modeling studies in autosomal dominant polycystic kidney disease (ADPKD).

Methods

We built the ADPKD cohort by extracting the relevant electronic health record data from nationwide Veterans Health Administration database (years 1999–2020).

Results

We identified 12,217 patients diagnosed with ADPKD. By the end of the 20-year study period, 5342 patients with ADPKD were deceased, 1583 were alive but reached ESKD, and 4827 remained alive without ESKD. Most demographic characteristics of this ADPKD cohort resemble the total US veteran population. For example, 94% were male patients, 45% age 65 years or older, 85% non-Hispanic, and 66% white; however, 19% were Black/African Americans (versus 12% in the general veteran population; a relevant enrichment after considering age and sex distributions between races). The comorbidities overrepresented in the ADPKD cohort include hypertension (89% versus 50%), diabetes (32% versus 22%), depression (40% versus 10%), chronic obstructive pulmonary disease (30% versus 6%), and congestive heart failure (21% versus 1%). By contrast, obesity was underrepresented in veterans with ADPKD (30% versus 41%).

Conclusions

We established a large electronic medical record-based cohort of ADPKD veterans. Here, we provide initial analysis of its demographic, comorbidity, and key laboratory data.

Autosomal Dominant Polycystic Kidney Disease: Extrarenal Involvement

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder, but kidneys are not the only organs involved in this systemic disorder. Individuals with the condition may display additional manifestations beyond the renal system, involving the liver, pancreas, and brain in the context of cystic manifestations, while involving the vascular system, gastrointestinal tract, bones, and cardiac valves in the context of non-cystic manifestations. Despite kidney involvement remaining the main feature of the disease, thanks to longer survival, early diagnosis, and better management of kidney-related problems, a new wave of complications must be faced by clinicians who treated patients with ADPKD. Involvement of the liver represents the most prevalent extrarenal manifestation and has growing importance in the symptom burden and quality of life. Vascular abnormalities are a key factor for patients' life expectancy and there is still debate whether to screen or not to screen all patients. Arterial hypertension is often the earliest onset symptom among ADPKD patients, leading to frequent cardiovascular complications. Although cardiac valvular abnormalities are a frequent complication, they rarely lead to relevant problems in the clinical history of polycystic patients. One of the newest relevant aspects concerns bone disorders that can exert a considerable influence on the clinical course of these patients. This review aims to provide the "state of the art" among the extrarenal manifestation of ADPKD.

An Artificial Intelligence Generated Automated Algorithm to Measure Total Kidney Volume in ADPKD

Introduction

Accurate tools to inform individual prognosis in patients with autosomal dominant polycystic kidney disease (ADPKD) are lacking. Here, we report an artificial intelligence (AI)-generated method for routinely measuring total kidney volume (TKV).

Methods

An ensemble U-net algorithm was created using the nnUNet approach. The training and internal cross-validation cohort consisted of all 1.5T magnetic resonance imaging (MRI) data acquired using 5 different MRI scanners (454 kidneys, 227 scans) in the CYSTic consortium, which was first manually segmented by a single human operator. As an independent validation cohort, we utilized 48 sequential clinical MRI scans with reference results of manual segmentation acquired by 6 individual analysts at a single center. The tool was then implemented for clinical use and its performance analyzed.

Results

The training or internal validation cohort was younger (mean age 44.0 vs. 51.5 years) and the female-to-male ratio higher (1.2 vs. 0.94) compared to the clinical validation cohort. The majority of CYSTic patients had PKD1 mutations (79%) and typical disease (Mayo Imaging class 1, 86%). The median DICE score on the clinical validation data set between the algorithm and human analysts was 0.96 for left and right kidneys with a median TKV error of -1.8%. The time taken to manually segment kidneys in the CYSTic data set was 56 (±28) minutes, whereas manual corrections of the algorithm output took 8.5 (±9.2) minutes per scan.

Conclusion

Our AI-based algorithm demonstrates performance comparable to manual segmentation. Its rapidity and precision in real-world clinical cases demonstrate its suitability for clinical application.

PKD1 Truncating Mutations Accelerate eGFR Decline in Autosomal Dominant Polycystic Kidney Disease Patients

INTRODUCTION

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic disease characterized by the accumulation of fluid-filled cysts in the kidneys, leading to renal volume enlargement and progressive kidney function impairment. Disease severity, though, may vary due to allelic and genetic heterogeneity. This study aimed to determine genotype-phenotype correlations between PKD1 truncating and non-truncating mutations and kidney function decline in ADPKD patients.

METHODS

We established a single-center retrospective cohort study in Kuwait where we followed every patient with a confirmed PKD1-ADPKD diagnosis clinically and genetically. Renal function tests were performed annually. We fitted generalized additive mixed effects models with random intercepts for each individual to analyze repeated measures of kidney function across mutation type. We then calculated survival time to kidney failure in a cox proportional hazards model. Models were adjusted for sex, age at visit, and birth year.

RESULTS

The study included 22 truncating and 20 non-truncating (42 total) patients followed for an average of 6.6 years (range: 1-12 years). Those with PKD1 truncating mutations had a more rapid rate of eGFR decline (-4.7 mL/min/1.73 m2 per year; 95% CI: -5.0, -4.4) compared to patients with PKD1 non-truncating mutations (-3.5 mL/min/1.73 m2 per year; 95% CI: -4.0, -3.1) (p for interaction <0.001). Kaplan-Meier survival analysis of time to kidney failure showed that patients with PKD1 truncating mutations had a shorter renal survival time (median 51 years) compared to those with non-truncating mutations (median 56 years) (P for log-rank = 0.008).

CONCLUSION

In longitudinal and survival analyses, patients with PKD1 truncating mutations showed a faster decline in kidney function compared to patients PKD1 non-truncating mutations. Early identification of patients with PKD1 truncating mutations can, at best, inform early clinical interventions or, at least, help suggest aggressive monitoring.

Genetic testing in the evaluation of recipient candidates and living kidney donors

PURPOSE OF REVIEW

The aim of this study is to provide an overview of the role of genetic testing in the evaluation of kidney transplant candidates and living donors who may be at risk for heritable kidney disease. We focus our discussion on monogenic diseases, excluding renal diseases that have complex polygenic influences. Adoption of new technologies such as next-generation sequencing (NGS) with comprehensive gene panels has greatly enabled access to genetic testing recently; yet transplant professionals rarely receive adequate training in clinical genetics. In addition to a broad discussion of genetic testing, we hope to illustrate the thought processes and resources used in clinical genetic evaluation of recipient candidates and donors.

RECENT FINDINGS

Targeted renal genetic panels, whole exome and genome sequencing have greatly expanded our ability to test for pathogenic variants. Testing methods, analytic tools and the subsequent interpretation by the testing laboratory and treating physician impacts patient management and clinicians may lack the resources to practice in this new era of genomic medicine.

SUMMARY

The expansion of genomics into transplant medicine can provide improved diagnosis in transplant candidates and potentially disease prediction in living donors. Transplant professionals need to be familiar with emerging trends, promises and limitations of NGS-based testing.

Molecular genetic diagnosis of kidney ciliopathies: Lessons from interpreting genomic sequencing data and the requirement for accurate phenotypic data

INTRODUCTION

Massively parallel sequencing (MPS) techniques have made a major impact on the identification of the genetic basis of inherited kidney diseases such as the ciliopathy autosomal dominant polycystic kidney disease (ADPKD). Great care must be taken when analysing MPS data in isolation from accurate phenotypic information, as this can cause misdiagnosis.

METHODS

Here, we describe a family trio, recruited to the Genomics England 100,000 Genomes Project, labelled as having cystic kidney disease, who were genetically unsolved following routine data analysis pipelines. We performed a bespoke reanalysis of Whole Genome Sequencing (WGS) data and coupled this with revised phenotypic data and targeted PCR and Sanger sequencing to provide a precise molecular genetic diagnosis.

RESULTS

We detected a heterozygous PKD1 frameshift variant within the WGS data which segregated with the redefined ADPKD phenotypes. An additional heterozygous exon deletion in ALG8 was also found in affected and unaffected individuals, but its precise clinical significance remains unclear.

CONCLUSION

This case illustrates that reanalysis of WGS data in unsolved cases of cystic kidney disease is valuable. Clinical phenotypes must be reassessed as these may have been incorrectly recorded and evolve over time. Undertaking additional studies including genotype-phenotype correlation in wider family members provides useful diagnostic information.

Real-life use of tolvaptan in ADPKD: a retrospective analysis of a large Canadian cohort

Tolvaptan is the first disease-modifying drug proven to slow eGFR decline in high-risk patients with ADPKD. However, barriers from the patient perspective to its use in real-life settings have not been systemically examined in a large cohort. This was a single-center, retrospective study of 523 existing or new patients with ADPKD followed at the Center for Innovative Management of PKD in Toronto, Ontario, between January 1, 2016 to December 31, 2018. All patients underwent clinical assessment including total kidney volume measurements and Mayo Clinic Imaging Class (MCIC). Those who were deemed to be at high risk were offered tolvaptan with their preference (yes or no) and reasons for their choices recorded. Overall, 315/523 (60%) patients had MCIC 1C-1E; however, only 96 (30%) of them were treated with tolvaptan at their last follow-up. Among these high-risk patients, those not treated versus treated with tolvaptan were more likely to have a higher eGFR (82 ± 26 vs. 61 ± 27 ml/min/1.73 m2), CKD stages 1-2 (79% vs. 41%), and MCIC 1C (63% vs. 31%). The most common reasons provided for not taking tolvaptan were lifestyle preference related to the aquaretic effect (51%), older age ≥ 60 (12%), and pregnancy/family planning (6%). In this real-world experience, at least 60% of patients with ADPKD considered to be at high risk for progression to ESKD by imaging were not treated with tolvaptan; most of them had early stages of CKD with well-preserved eGFR and as such, were prime targets for tolvaptan therapy to slow disease progression. Given that the most common reason for tolvaptan refusal was the concern for intolerability of the aquaretic side-effect, strategies to mitigate this may help to reduce this barrier to tolvaptan therapy.

ADPKD-Causing Missense Variants in Polycystin-1 Disrupt Cell Surface Localization or Polycystin Channel Function

Autosomal dominant polycystic kidney disease (ADPKD) is the leading monogenic cause of kidney failure and affects millions of people worldwide. Despite the prevalence of this monogenic disorder, our limited mechanistic understanding of ADPKD has hindered therapeutic development. Here, we successfully developed bioassays that functionally classify missense variants in polycystin-1 (PC1). Strikingly, ADPKD pathogenic missense variants cluster into two major categories: 1) those that disrupt polycystin cell surface localization or 2) those that attenuate polycystin ion channel activity. We found that polycystin channels with defective surface localization could be rescued with a small molecule. We propose that small-molecule-based strategies to improve polycystin cell surface localization and channel function will be effective therapies for ADPKD patients.

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.

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.

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.

Dialysis and Transplant Considerations in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the fourth leading cause of kidney replacement therapy. Unfortunately, the need for dialysis or kidney transplantation is a foreseeable outcome for many patients affected by ADPKD. We review some of the unique issues that should be considered in the management of patients with ADPKD who require dialysis or kidney transplantation. The choice of dialysis modality may be influenced by the enlarged kidneys and liver, but peritoneal dialysis should not be excluded as an option, as studies do not consistently show that there is an increased risk for technique failure or peritonitis. The optimal kidney replacement therapy option remains kidney transplantation; however, nephrectomy may be needed if there is insufficient space for the allograft. Living donor candidates from at-risk families need to be excluded from carrying the disease either by diagnostic imaging criteria or genetic testing. Other potential transplant issues, such as malignancy and cardiovascular and metabolic risks, should also be recognized. Despite these issues, patients with ADPKD requiring dialysis or kidney transplantation generally have more favorable outcomes as compared to those with other causes of chronic kidney disease. Further studies are still needed to personalize the therapeutic approach for those receiving kidney replacement therapy and eventually improve clinical outcomes.

Baseline characteristics of the Korean genetic cohort of inherited cystic kidney disease

BACKGROUND

Identifying genetic mutations in individuals with inherited cystic kidney disease is necessary for precise treatment. We aimed to elucidate the genetic characteristics of cystic kidney disease in the Korean population.

METHODS

We conducted a 3-year prospective, multicenter cohort study at eight hospitals from May 2019 to May 2022. Patients with more than three renal cysts were enrolled and classified into two categories, typical autosomal dominant polycystic kidney disease (ADPKD) and atypical PKD. We identified the clinical characteristics and performed a genetic analysis using a targeted gene panel.

RESULTS

A total of 725 adult patients were included in the study, of which 560 (77.2%) were diagnosed with typical ADPKD and 165 (22.8%) had atypical PKD. Among the typical ADPKD cases, the Mayo imaging classification was as follows: 1A (55, 9.9%), 1B (149, 26.6%), 1C (198, 35.8%), 1D (90, 16.3%), and 1E (61, 11.0%). The atypical PKD cases were classified as bilateral cystic with bilateral atrophic (31, 37.3%), lopsided (27, 32.5%), unilateral (nine, 10.8%), segmental (eight, 9.6%), bilateral cystic with unilateral atrophic (seven, 8.4%), and asymmetric (one, 1.2%). Pathogenic variants were found in 64.3% of the patients using the ciliopathy-related targeted gene panel. The typical ADPKD group demonstrated a higher discovery rate (62.3%) than the atypical PKD group (41.8%).

CONCLUSION

We present a nationwide genetic cohort's baseline clinical and genetic characteristics for Korean cystic kidney disease.

Cleavage fragments of the C-terminal tail of polycystin-1 are regulated by oxidative stress and induce mitochondrial dysfunction

Mutations in the gene encoding polycystin-1 (PC1) are the most common cause of autosomal dominant polycystic kidney disease (ADPKD). Cysts in ADPKD exhibit a Warburg-like metabolism characterized by dysfunctional mitochondria and aerobic glycolysis. PC1 is an integral membrane protein with a large extracellular domain, a short C-terminal cytoplasmic tail and shares structural and functional similarities with G protein-coupled receptors. Its exact function remains unclear. The C-terminal cytoplasmic tail of PC1 undergoes proteolytic cleavage, generating soluble fragments that are overexpressed in ADPKD kidneys. The regulation, localization, and function of these fragments is poorly understood. Here, we show that a ∼30 kDa cleavage fragment (PC1-p30), comprising the entire C-terminal tail, undergoes rapid proteasomal degradation by a mechanism involving the von Hippel-Lindau tumor suppressor protein. PC1-p30 is stabilized by reactive oxygen species, and the subcellular localization is regulated by reactive oxygen species in a dose-dependent manner. We found that a second, ∼15 kDa fragment (PC1-p15), is generated by caspase cleavage at a conserved site (Asp-4195) on the PC1 C-terminal tail. PC1-p15 is not subject to degradation and constitutively localizes to the mitochondrial matrix. Both cleavage fragments induce mitochondrial fragmentation, and PC1-p15 expression causes impaired fatty acid oxidation and increased lactate production, indicative of a Warburg-like phenotype. Endogenous PC1 tail fragments accumulate in renal cyst-lining cells in a mouse model of PKD. Collectively, these results identify novel mechanisms regarding the regulation and function of PC1 and suggest that C-terminal PC1 fragments may be involved in the mitochondrial and metabolic abnormalities observed in ADPKD.

A novel heterozygous PKD1 variant causing alternative splicing in a Chinese family with autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by pathogenic variants of PKD1 and PKD2. Compared to PKD2-related patients, patients with PKD1 pathogenic variants have more severe symptoms, present a gradual decline in renal function, and finally progress to end-stage kidney disease with an earlier mean onset age.

METHODS

In this study, trio exome sequencing (ES) was performed to reveal the genetic etiology in a Chinese family clinically diagnosed with polycystic kidney, followed by validation through Sanger sequencing on both genomic DNA and cDNA levels. Subsequently, targeted preimplantation genetic testing was provided for the family.

RESULTS

A novel heterozygous PKD1 variant (c.1717_1722+11del) was detected in the proband and other clinically-affected relatives. Interestingly, cDNA sequencing demonstrated that the variant, despite being annotated as non-frameshift within exon 8, impacted the splicing of PKD1. Two abnormal transcription products were formed: one induced frameshift, while the other caused 133 amino acids to be inserted between exon 8 and exon 9.

CONCLUSIONS

Our study revealed a novel PKD1 variant using ES as the cause of ADPKD in a Chinese family with multiple affected members. The variant at the exon-intron boundary would induce alternative splicing, which should not be excluded from genetic analysis. Validated on the cDNA level could provide more comprehensive genetic information for disease stratification. And the novel variant expands the spectrum of PKD1 variants in ADPKD. The recurrent risk could be blocked accordingly for the families' offspring.

Clinical Quality Control of MRI Total Kidney Volume Measurements in Autosomal Dominant Polycystic Kidney Disease

Total kidney volume measured on MRI is an important biomarker for assessing the progression of autosomal dominant polycystic kidney disease and response to treatment. However, we have noticed that there can be substantial differences in the kidney volume measurements obtained from the various pulse sequences commonly included in an MRI exam. Here we examine kidney volume measurement variability among five commonly acquired MRI pulse sequences in abdominal MRI exams in 105 patients with ADPKD. Right and left kidney volumes were independently measured by three expert observers using model-assisted segmentation for axial T2, coronal T2, axial single-shot fast spin echo (SSFP), coronal SSFP, and axial 3D T1 images obtained on a single MRI from ADPKD patients. Outlier measurements were analyzed for data acquisition errors. Most of the outlier values (88%) were due to breathing during scanning causing slice misregistration with gaps or duplication of imaging slices (n = 35), slice misregistration from using multiple breath holds during acquisition (n = 25), composing of two overlapping acquisitions (n = 17), or kidneys not entirely within the field of view (n = 4). After excluding outlier measurements, the coefficient of variation among the five measurements decreased from 4.6% pre to 3.2%. Compared to the average of all sequences without errors, TKV measured on axial and coronal T2 weighted imaging were 1.2% and 1.8% greater, axial SSFP was 0.4% greater, coronal SSFP was 1.7% lower and axial T1 was 1.5% lower than the mean, indicating intrinsic measurement biases related to the different MRI contrast mechanisms. In conclusion, MRI data acquisition errors are common but can be identified using outlier analysis and excluded to improve organ volume measurement consistency. Bias toward larger volume measurements on T2 sequences and smaller volumes on axial T1 sequences can also be mitigated by averaging data from all error-free sequences acquired.

Cystic Kidney Diseases in Children and Adults: Differences and Gaps in Clinical Management

Cystic kidney diseases, when broadly defined, have a wide differential diagnosis extending from recessive diseases with a prenatal or pediatric diagnosis, to the most common autosomal-dominant polycystic kidney disease primarily affecting adults, and several other genetic or acquired etiologies that can manifest with kidney cysts. The most likely diagnoses to consider when assessing a patient with cystic kidney disease differ depending on family history, age stratum, radiologic characteristics, and extrarenal features. Accurate identification of the underlying condition is crucial to estimate the prognosis and initiate the appropriate management, identification of extrarenal manifestations, and counseling on recurrence risk in future pregnancies. There are significant differences in the clinical approach to investigating and managing kidney cysts in children compared with adults. Next-generation sequencing has revolutionized the diagnosis of inherited disorders of the kidney, despite limitations in access and challenges in interpreting the data. Disease-modifying treatments are lacking in the majority of kidney cystic diseases. For adults with rapid progressive autosomal-dominant polycystic kidney disease, tolvaptan (V2-receptor antagonist) has been approved to slow the rate of decline in kidney function. In this article, we examine the differences in the differential diagnosis and clinical management of cystic kidney disease in children versus adults, and we highlight the progress in molecular diagnostics and therapeutics, as well as some of the gaps meriting further attention.

PKD1 Mutation Is a Biomarker for Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) occurs in 1 in 500-4000 people worldwide. Genetic mutation is a biomarker for predicting renal dysfunction in patients with ADPKD. In this study, we performed a genetic analysis of Japanese patients with ADPKD to investigate the prognostic utility of genetic mutations in predicting renal function outcomes.

METHODS

Patients clinically diagnosed with ADPKD underwent a panel genetic test for germline mutations in PKD1 and PKD2. This study was conducted with the approval of the Ethics Committee of Juntendo University (no. 2019107).

RESULTS

Of 436 patients, 366 (83.9%) had genetic mutations. Notably, patients with PKD1 mutation had a significantly decreased ΔeGFR/year compared to patients with PKD2 mutation, indicating a progression of renal dysfunction (-3.50 vs. -2.04 mL/min/1.73 m²/year, p = 0.066). Furthermore, PKD1 truncated mutations had a significantly decreased ΔeGFR/year compared to PKD1 non-truncated mutations in the population aged over 65 years (-6.56 vs. -2.16 mL/min/1.73 m²/year, p = 0.049). Multivariate analysis showed that PKD1 mutation was a more significant risk factor than PKD2 mutation (odds ratio, 1.81; 95% confidence interval, 1.11-3.16; p = 0.020).

CONCLUSIONS

The analysis of germline mutations can predict renal prognosis in Japanese patients with ADPKD, and PKD1 mutation is a biomarker of ADPKD.

Molecular Diagnosis and Identification of Novel Pathogenic Variants in a Large Cohort of Italian Patients Affected by Polycystic Kidney Diseases

Polycystic Kidney Diseases (PKDs) consist of a genetically and phenotypically heterogeneous group of inherited disorders characterized by numerous renal cysts. PKDs include autosomal dominant ADPKD, autosomal recessive ARPKD and atypical forms. Here, we analyzed 255 Italian patients using an NGS panel of 63 genes, plus Sanger sequencing of exon 1 of the PKD1 gene and MPLA (PKD1, PKD2 and PKHD1) analysis. Overall, 167 patients bore pathogenic/likely pathogenic variants in dominant genes, and 5 patients in recessive genes. Four patients were carriers of one pathogenic/likely pathogenic recessive variant. A total of 24 patients had a VUS variant in dominant genes, 8 patients in recessive genes and 15 patients were carriers of one VUS variant in recessive genes. Finally, in 32 patients we could not reveal any variant. Regarding the global diagnostic status, 69% of total patients bore pathogenic/likely pathogenic variants, 18.4% VUS variants and in 12.6% of patients we could not find any. PKD1 and PKD2 resulted to be the most mutated genes; additional genes were UMOD and GANAB. Among recessive genes, PKHD1 was the most mutated gene. An analysis of eGFR values showed that patients with truncating variants had a more severe phenotype. In conclusion, our study confirmed the high degree of genetic complexity at the basis of PKDs and highlighted the crucial role of molecular characterization in patients with suspicious clinical diagnosis. An accurate and early molecular diagnosis is essential to adopt the appropriate therapeutic protocol and represents a predictive factor for family members.

Modifiers of Autosomal Dominant Polycystic Kidney Disease Severity: The Role of PKD1 Hypomorphic Alleles

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic cause of kidney failure in adult life. Rarely, ADPKD can be diagnosed in utero or in infancy, and the genetic mechanism underlying such severe presentation has been shown to be related to reduced gene dosage. Biallelic PKD1 variants are often identified in early onset ADPKD, with one main pathogenic variant and a modifier hypomorphic variant showing an in trans configuration. We describe two unrelated individuals with early onset cystic kidney disease and unaffected parents, where a combination of next-generation sequencing of cystic genes including PKHD1, HNF1B and PKD1 allowed the identification of biallelic PKD1 variants. Furthermore, we review the medical literature in order to report likely PKD1 hypomorphic variants reported to date and estimate a minimal allele frequency of 1/130 for this category of variants taken as a group. This figure could help to orient genetic counseling, although the interpretation and the real clinical impact of rare PKD1 missense variants, especially if previously unreported, remain challenging.

An update on treatments for autosomal dominant polycystic kidney disease

ABSTRACT

Autosomal dominant polycystic kidney disease (ADPKD) is less common than primary hypertension or diabetes but should be considered as a possible cause of end-stage renal disease, especially in young patients without comorbidities. Because of ADPKD's nonspecific symptoms, the diagnosis, treatment, and pertinent patient education may be delayed. This article describes ADPKD and its management, including tolvaptan, a new treatment with the potential to reduce or delay morbidity. However, only a subset of patients qualifies for this expensive treatment.

Association of polygenic scores with chronic kidney disease phenotypes in a longitudinal study of older adults

Risk of chronic kidney disease (CKD) is influenced by environmental and genetic factors and increases sharply in individuals 70 years and older. Polygenic scores (PGS) for kidney disease-related traits have shown promise but require validation in well-characterized cohorts. Here, we assessed the performance of recently developed PGSs for CKD-related traits in a longitudinal cohort of healthy older individuals enrolled in the Australian ASPREE randomized controlled trial of daily low-dose aspirin with CKD risk at baseline and longitudinally. Among 11,813 genotyped participants aged 70 years or more with baseline eGFR measures, we tested associations between PGSs and measured eGFR at baseline, clinical phenotype of CKD, and longitudinal rate of eGFR decline spanning up to six years of follow-up per participant. A PGS for eGFR was associated with baseline eGFR, with a significant decrease of 3.9 mL/min/1.73m2 (95% confidence interval -4.17 to -3.68) per standard deviation (SD) increase of the PGS. This PGS, as well as a PGS for CKD stage 3 were both associated with higher risk of baseline CKD stage 3 in cross-sectional analysis (Odds Ratio 1.75 per SD, 95% confidence interval 1.66-1.85, and Odds Ratio 1.51 per SD, 95% confidence interval 1.43-1.59, respectively). Longitudinally, two separate PGSs for eGFR slope were associated with significant kidney function decline during follow-up. Thus, our study demonstrates that kidney function has a considerable genetic component in older adults, and that new PGSs for kidney disease-related phenotypes may have potential utility for CKD risk prediction in advanced age.

PKD1 Nonsense Variant in a Lagotto Romagnolo Family with Polycystic Kidney Disease

A female Lagotto Romagnolo dog with polycystic kidney disease (PKD) and her progeny, including PKD-affected offspring, were studied. All affected dogs appeared clinically inconspicuous, while sonography revealed the presence of renal cysts. The PKD-affected index female was used for breeding and produced two litters with six affected offspring of both sexes and seven unaffected offspring. The pedigrees suggested an autosomal dominant mode of inheritance of the trait. A trio whole genome sequencing analysis of the index female and her unaffected parents identified a de novo heterozygous nonsense variant in the coding region of the PKD1 gene. This variant, NM_001006650.1:c.7195G>T, is predicted to truncate 44% of the open reading frame of the wild-type PKD1 protein, NP_001006651.1:p.(Glu2399*). The finding of a de novo variant in an excellent functional candidate gene strongly suggests that the PKD1 nonsense variant caused the observed phenotype in the affected dogs. Perfect co-segregation of the mutant allele with the PKD phenotype in two litters supports the hypothesized causality. To the best of our knowledge, this is the second description of a PKD1-related canine form of autosomal dominant PKD that may serve as an animal model for similar hepatorenal fibrocystic disorders in humans.

Mutation Analysis of PKD1 and PKD2 Genes in a Large Italian Cohort Reveals Novel Pathogenic Variants Including a Novel Complex Rearrangement

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited disease of the kidney. It occurs in adulthood but is also rarely diagnosed in early childhood. The majority of the disease-causing variants observed in ADPKD patients are in two genes: PKD1 and PKD2.

METHODS

237 patients from 198 families with a clinical diagnosis of ADPKD were screened for PKD1 and PKD2 genetic variants using Sanger sequencing and multiple ligation-dependent probe amplification analysis.

RESULTS

Disease-causing (diagnostic) variants were identified in 173 families (211 patients), 156 on PKD1 and 17 on PKD2. Variants of unknown significance were detected in 6 additional families, while no mutations were found in the remaining 19 families. Among the diagnostic variants detected, 51 were novel. In ten families, seven large rearrangements were found and the molecular breakpoints of 3 rearrangements were identified. Renal survival was significantly worse for PKD1-mutated patients, particularly those carrying truncating mutations. In patients with PKD1 truncating (PKD1-T) mutations, disease onset was significantly earlier than in patients with PKD1 non-truncating variants or PKD2-mutated patients.

CONCLUSIONS

Comprehensive genetic testing confirms its utility in diagnosing patients with ADPKD and contributes to explaining the clinical heterogeneity observed in this disease. Moreover, the genotype-phenotype correlation can allow for a more accurate disease prognosis.

Genomics in the kidney clinic

Inherited diseases are a frequent cause of end-stage kidney disease and often seen in the kidney clinic. Clinical genomic testing is increasingly available in the UK and eligible patients in England can be referred through the NHS Genomic Medicine Service. Testing is useful for diagnosis, prognostication and management of conditions such as autosomal dominant polycystic kidney disease (ADPKD), Alport syndrome, autosomal dominant tubulointerstitial kidney disease (ADTKD) and focal segmental glomerulosclerosis (FSGS). As more patients undergo genomic testing and newer technologies such as whole genome sequencing are applied, we are developing a greater appreciation of the full phenotypic spectrum of inherited kidney diseases and the challenges associated with the interpretation of clinically significant variants.

Autosomal Dominant Polycystic Kidney Disease in Children and Adolescents: Assessing and Managing Risk of Progression

The clinical management of autosomal dominant polycystic kidney disease (ADPKD) in adults has shifted from managing complications to delaying disease progression through newly emerging therapies. Regarding pediatric management of the disease, there are still specific hurdles related to the management of children and adolescents with ADPKD and, unlike adults, there are no specific therapies for pediatric ADPKD or stratification models to identify children and young adults at risk of rapid decline in kidney function. Therefore, early identification and management of factors that may modify disease progression, such as hypertension and obesity, are of most importance for young children with ADPKD. Many of these risk factors could promote disease progression in both ADPKD and chronic kidney disease. Hence, nephroprotective measures applied early in life can represent a window of opportunity to prevent the decline of the glomerular filtration rate especially in young patients with ADPKD. In this review, we highlight current challenges in the management of patients with pediatric ADPKD, the importance of early modifying factors in disease progression as well as the gaps and future perspectives in the pediatric ADPKD research field.

Predicting the Risk of Progression in Indian ADPKD Cohort using PROPKD Score - A Single-Center Retrospective Study

Background

With the variable genotype-phenotype expression of autosomal dominant polycystic kidney disease (ADPKD) and availability of novel targeted therapies, it is important to find predictors for rapid progression. The PROPKD score, consisting of genetic and clinical parameters like sex, hypertension, and urological events, is a useful tool in predicting the risk of progression. This study was aimed to determine the risk of ADPKD progression in Indian patients using the PROPKD score.

Materials and Methods

A retrospective study was done from 2006 to 2021. ADPKD patients with ESRD were included in the study. Scoring was done as per the PROPKD score as follows: male sex: 1, onset of hypertension before 35 years: 2, first urological event before 35 years: 2, PKD1 truncating mutation: 4, PKD1 non-truncating mutation: 2, and PKD2 mutation: 0. Two types of risk classifications were done as follows: (a) considering the clinical variables in all 73 patients (male sex, onset of hypertension before 35 years, and first urological event before 35 years), they were classified into three risk groups: low-risk group (0-1), intermediate-risk group (2-3), and high-risk group (4-5) and (b) considering the clinical variables and type of mutation in 39 patients, they were classified into three risk groups: low-risk group (0-3), intermediate-risk group (4-6), and high-risk group (7-9).

Results

Total number of patients included was 73, with the median age at ESRD being 54 years. High-risk group of clinical variables with hazard ratio (HR) of 4.570 (2.302-9.075, P < 0.001) and high-risk group of the PROPKD score with HR of 6.594 (1.868-23.284, P = 0.003) were associated with early ESRD. High-risk groups of both classifications were associated with early ESRD.

Conclusion

High-risk groups based on the PROPKD scoring and clinical variables were associated with early progression to ESRD.

OVERTURE: A Worldwide, Prospective, Observational Study of Disease Characteristics in Patients With ADPKD

Introduction

The course of autosomal dominant polycystic kidney disease (ADPKD) varies greatly among affected individuals, necessitating natural history studies to characterize the determinants and effects of disease progression. Therefore, we conducted an observational, longitudinal study (OVERTURE; NCT01430494) of patients with ADPKD.

Methods

This prospective study enrolled a large international population (N = 3409) encompassing a broad spectrum of ages (12-78 years), chronic kidney disease (CKD) stages (G1-G5), and Mayo imaging classifications (1A-1E). Outcomes included kidney function, complications, quality of life, health care resource utilization, and work productivity.

Results

Most subjects (84.4%) completed ≥12 months of follow-up. Consistent with earlier findings, each additional l/m of height-adjusted total kidney volume (htTKV) on magnetic resonance imaging (MRI) was associated with worse outcomes, including lower estimated glomerular filtration rate (eGFR) (regression coefficient 17.02, 95% confidence interval [CI] 15.94-18.11) and greater likelihood of hypertension (odds ratio [OR] 1.25, 95% CI 1.17-1.34), kidney pain (OR 1.22, 95% CI 1.11-1.33), and hematuria (OR 1.35, 95% CI 1.21-1.51). Greater baseline htTKV was also associated with worse patient-reported health-related quality of life (e.g., ADPKD Impact Scale physical score, regression coefficient 1.02, 95% CI 0.65-1.39), decreased work productivity (e.g., work days missed, regression coefficient 0.55, 95% CI 0.18-0.92), and increased health care resource utilization (e.g., hospitalizations, OR 1.48, 95% CI 1.33-1.64) during follow-up.

Conclusion

Although limited by a maximum 3-year duration of follow-up, this observational study characterized the burden of ADPKD in a broad population and indicated the predictive value of kidney volume for outcomes other than kidney function.

Blocker displacement amplification-based genetic diagnosis for autosomal dominant polycystic kidney disease and the clinical outcomes of preimplantation genetic testing

OBJECTIVE

Given that the molecular diagnosis of autosomal dominant polycystic kidney disease (ADPKD) is complicated, we aim to apply blocker displacement amplification (BDA) on the mutational screening of PKD1 and PKD2.

METHODS

A total of 35 unrelated families with ADPKD were recruited from the Center for Reproductive Medicine, Women and Children's Hospital of Chongqing Medical University (Chongqing, China), from October 2018 to October 2021. Long-range PCR followed by next-generation sequencing were applied for resequencing of PKD1 and PKD2, and the putatively disease-causative variants were verified with BDA. The effects of ADPKD on male and female infertility and the factors influencing the clinical outcomes of preimplantation genetic testing (PGT) for ADPKD were investigated.

RESULTS

A total of 26 PKD1 variants and 5 PKD2 variants were identified, of which 13 were newly discovered. The BDA system worked effectively for eliminating the interference of pseudogenes in genetic testing of PKD1 (1-33 exons) with different concentrations of genome DNA. The females with ADPKD have no specific infertility factors, while 68.2% of the affected men were with abnormal sperm concentration and/or motility with an indefinite genotype-phenotype relationship. As for PGT, the fertilization rate of couples with the male partner having ADPKD was relatively lower compared to those with the female partner being affected. The ADPKD patients receiving PGT usually achieved high rates of live births.

CONCLUSION

These findings expanded the variant spectrum of PKD genes and emphasized the application prospect of blocker displacement amplification on PKD1-related genetic diagnosis.

Probenecid slows disease progression in a murine model of autosomal dominant polycystic kidney disease

Development of autosomal dominant polycystic kidney disease (ADPKD) involves renal epithelial cell abnormalities. Cystic fluid contains a high level of ATP that, among other effects, leads to a reduced reabsorption of electrolytes in cyst-lining cells, and thus results in cystic fluid accumulation. Earlier, we demonstrated that Pkd1RC/RC mice, a hypomorphic model of ADPKD, exhibit increased expression of pannexin-1, a membrane channel capable of ATP release. In the current study, we found that human ADPKD cystic epithelia have higher pannexin-1 abundance than normal collecting ducts. We hypothesized that inhibition of pannexin-1 function with probenecid can be used to attenuate ADPKD development. Renal function in male and female Pkd1RC/RC and control mice was monitored between 9 and 20 months of age. To test the therapeutic effects of probenecid (a uricosuric agent and a pannexin-1 blocker), osmotic minipumps were implanted in male and female Pkd1RC/RC mice, and probenecid or vehicle was administered for 42 days until 1 year of age. Probenecid treatment improved glomerular filtration rates and slowed renal cyst formation in male mice (as shown in histopathology). The mechanistic effects of probenecid on sodium reabsorption and fluid transport were tested on polarized mpkCCDcl4 cells subjected to short-circuit current measurements, and in 3D cysts grown in Matrigel. In the mpkCCDcl4 epithelial cell line, probenecid elicited higher ENaC currents and attenuated in vitro cyst formation, indicating lower sodium and less fluid retention in the cysts. Our studies open new avenues of research into targeting pannexin-1 in ADPKD pathology.

A Low-Cost Sequencing Platform for Rapid Genotyping in ADPKD and its Impact on Clinical Care

Introduction

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common genetic cause of kidney failure. Because of the heterogeneity in disease progression in ADPKD, parameters predicting future outcome are important. The disease-causing genetic variant is one of these parameters.

Methods

A multiplex polymerase chain reaction (PCR)-based panel (MPP) was established for analysis of 6 polycystic kidney disease (PKD) genes (PKD1, PKD2, HNF1B, GANAB, DZIP1L, and PKHD1) in 441 patients with ADPKD. Selected patients were additionally sequenced using Sanger sequencing or a custom enrichment-based gene panel. Results were combined with clinical characteristics to assess the impact of genetic data on clinical decision-making. Variants of unclear significance (VUS) were considered diagnostic based on a classic ADPKD clinical phenotype.

Results

Using the MPP, disease-causing variants were detected in 65.3% of patients. Sanger sequencing and the custom gene panel in 32 patients who were MPP-negative revealed 20 variants missed by MPP, (estimated overall false negative rate 24.6%, false-positive rate 9.4%). Combining clinical and genetic data revealed that knowledge of the genotype could have impacted the treatment decision in 8.2% of patients with a molecular genetic diagnosis. Sequencing only the PKD1 pseudogene homologous region in MPP-negative patients resulted in an acceptable false-negative rate of 3.28%.

Conclusion

The MPP yields rapid genotype information at lower costs and allows for simple extension of the panel for new disease genes. Additional sequencing of the PKD1 pseudogene homologous region is required in negative cases. Access to genotype information even in settings with limited resources is important to allow for optimal patient counseling in ADPKD.

Cystic Diseases of the Kidneys: From Bench to Bedside

Exploration into the causes of hereditary renal cystic diseases demonstrates a deep-rooted connection with the proteomic components of the cellular organelle cilia. Cilia are essential to the signaling cascades, and their dysfunction has been tied to a range of renal cystic diseases initiating with studies on the oak ridge polycystic kidney (ORPK) mouse model. Here, we delve into renal cystic pathologies that have been tied with ciliary proteosome and highlight the genetics associated with each. The pathologies are grouped based on the mode of inheritance, where inherited causes that result in cystic kidney disease phenotypes include autosomal dominant and autosomal recessive polycystic kidney disease, nephronophthisis (Bardet-Biedl syndrome and Joubert Syndrome), and autosomal dominant tubulointerstitial kidney disease. Alternatively, phakomatoses-, also known as neurocutaneous syndromes, associated cystic kidney diseases include tuberous sclerosis (TS) and Von Hippel-Lindau (VHL) disease. Additionally, we group the pathologies by the mode of inheritance to discuss variations in recommendations for genetic testing for biological relatives of a diagnosed individual.

The genetic landscape of autosomal dominant polycystic kidney disease in Kuwait

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal monogenic disease, characterized by bilateral accumulation of renal fluid-filled cysts leading to progressive renal volume enlargement and gradual impairment of kidney function, often resulting in end-stage renal disease. Kuwait could provide valuable genetic insights about ADPKD, including intrafamilial phenotypic variation, given its large household size. This study aims to provide a comprehensive description of the pathogenic variants linked to ADPKD in the Kuwaiti population using multiple genetic analysis modalities and to describe and analyse the ADPKD phenotypic spectrum in terms of kidney function, kidney volume and renal survival.

Methods

A total of 126 ADPKD patients from 11 multiplex families and 25 singletons were recruited into the study. A combination of targeted next-generation sequencing (tNGS), long-range polymerase chain reaction, Sanger sequencing and multiplex ligation-dependent probe amplification were utilized for genetic diagnosis. Clinical evaluation was conducted through renal function testing and ultrasonographic kidney volume analysis.

Results

We identified 29 ADPKD pathogenic mutations from 36 families achieving an overall molecular genetic diagnostic rate of 112/126 (88.9%), including 29/36 (80.6%) in families. A total of 28/36 (77.8%) families had pathogenic mutations in PKD1, of which 17/28 (60.7%) were truncating, and 1/36 (2.8%) had a pathogenic variant in the IFT140 gene. A total of 20/29 (69%) of the identified ADPKD mutations were novel and described for the first time, including a TSC2-PKD1 contiguous syndrome. Clinical analysis indicated that genetically unresolved ADPKD cases had no apparent association between kidney volume and age.

Conclusion

We describe for the first time the genetic landscape of ADPKD in Kuwait. The observed genetic heterogeneity underlining ADPKD along with the wide phenotypic spectrum reveal the level of complexity in disease pathophysiology. ADPKD genetic testing could improve the care of patients through improved disease prognostication, guided treatment and genetic counselling. However, to fulfil the potential of genetic testing, it is important to overcome the hurdle of genetically unresolved ADPKD cases.

The Clinical and Mutational Spectrum of 69 Turkish Children with Autosomal Recessive or Autosomal Dominant Polycystic Kidney Disease: A Multicenter Retrospective Cohort Study

INTRODUCTION

Autosomal recessive polycystic kidney disease (ARPKD) is associated with pathogenic variants in the PKHD1 gene. Autosomal dominant polycystic kidney disease (ADPKD) is mainly associated with pathogenic variants in PKD1 or PKD2. The present study aimed to identify the clinical and genetic features of Turkish pediatric ARPKD and ADPKD patients.

METHODS

This multicenter, retrospective cohort study included 21 genetically confirmed ARPKD and 48 genetically confirmed ADPKD patients from 7 pediatric nephrology centers. Demographic features, clinical, and laboratory findings at presentation and during 12-month intervals were recorded.

RESULTS

The median age of the ARPKD patients at diagnosis was lower than the median age of ADPKD patients (10.5 months [range: 0-15 years] vs. 5.2 years [range: 0.1-16 years], respectively, [p = 0.014]). At the time of diagnosis, the median eGFR in the ARPKD patients was lower compared to that of ADPKD patients (81.6 [IQR: 28.7-110.5] mL/min/1.73 m2 and 118 [IQR: 91.2-139.8] mL/min/1.73 m2, respectively, [p = 0.0001]). In total, 11 (52.4%) ARPKD patients had malnutrition; 7 (33.3%) patients had growth retardation at presentation; and 4 (19%) patients had both malnutrition and growth retardation. At diagnosis, 8 (16.7%) of the ADPKD patients had malnutrition, and 5 (10.4%) patients had growth retardation. The malnutrition, growth retardation, and hypertension rates at diagnosis were higher in the ARPKD patients than the ADPKD patients (p = 0.002, p = 0.02, and p = 0.0001, respectively). ARPKD patients with malnutrition and growth retardation had worse renal survival compared to the patients without (p = 0.03 and p = 0.01). Similarly, ADPKD patients with malnutrition had worse renal survival compared to the patients without (p = 0.002). ARPKD patients with truncating variants had poorer 3- and 6-year renal outcome than those carrying non-truncating variants (p = 0.017).

CONCLUSION

Based on renal survival analysis, type of genetic variant, growth retardation, and/or malnutrition at presentation were observed to be factors associated with progression to chronic kidney disease (CKD). Differentiation of ARPKD and ADPKD, and identification of the predictors of the development of CKD are vital for optimal management of patients with ARPKD or ADPKD.