Autosomal Dominant Polycystic Kidney Disease (ADPKD) affects up to 12 million individuals and is the 4th most common cause for renal replacement therapy worldwide. There have been many recent advances in the understanding of its molecular genetics and biology, and in the diagnosis and management of its manifestations. Yet, diagnosis, evaluation, prevention and treatment vary widely and there are no broadly accepted practice guidelines. Barriers to translation of basic science breakthroughs to clinical care exist, with considerable heterogeneity across countries. The KDIGO Controversies Conference on ADPKD brought together a panel of multi-disciplinary clinical expertise and engaged patients to identify areas of consensus, gaps in knowledge, and research and health care priorities related to diagnosis, monitoring of kidney disease progression, management of hypertension, renal function decline and complications, end-stage renal disease, extrarenal complications, and practical integrated patient support. These are summarized in this report.

Individuals who are at risk for autosomal dominant polycystic kidney disease are often screened by ultrasound using diagnostic criteria derived from individuals with mutations in PKD1. Families with mutations in PKD2 typically have less severe disease, suggesting a potential need for different diagnostic criteria. In this study, 577 and 371 at-risk individuals from 58 PKD1 and 39 PKD2 families, respectively, were assessed by renal ultrasound and molecular genotyping. Using sensitivity data derived from genetically affected individuals and specificity data derived from genetically unaffected individuals, various diagnostic criteria were compared. In addition, data sets were created to simulate the PKD1 and PKD2 case mix expected in practice to evaluate the performance of diagnostic criteria for families of unknown genotype. The diagnostic criteria currently in use performed suboptimally for individuals with mutations in PKD2 as a result of reduced test sensitivity. In families of unknown genotype, the presence of three or more (unilateral or bilateral) renal cysts is sufficient for establishing the diagnosis in individuals aged 15 to 39 y, two or more cysts in each kidney is sufficient for individuals aged 40 to 59 y, and four or more cysts in each kidney is required for individuals Ն60 yr. Conversely, fewer than two renal cysts in at-risk individuals aged Ն40 yr is sufficient to exclude the disease. These unified diagnostic criteria will be useful for testing individuals who are at risk for autosomal dominant polycystic kidney disease in the usual clinical setting in which molecular genotyping is seldom performed.

Among all randomly assigned patients (with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy), the percentage of patients who had a response at 6 months did not differ significantly between the migalastat group and the placebo group. (Funded by Amicus Therapeutics; ClinicalTrials.gov numbers, NCT00925301 [study AT1001-011] and NCT01458119 [study AT1001-041].).

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Alport syndrome inevitably leads to end-stage renal disease and there are no therapies known to improve outcome. Here we determined whether angiotensin-converting enzyme inhibitors can delay time to dialysis and improve life expectancy in three generations of Alport families. Patients were categorized by renal function at the initiation of therapy and included 33 with hematuria or microalbuminuria, 115 with proteinuria, 26 with impaired renal function, and 109 untreated relatives. Patients were followed for a period whose mean duration exceeded two decades. Untreated relatives started dialysis at a median age of 22 years. Treatment of those with impaired renal function significantly delayed dialysis to a median age of 25, while treatment of those with proteinuria delayed dialysis to a median age of 40. Significantly, no patient with hematuria or microalbuminuria advanced to renal failure so far. Sibling pairs confirmed these results, showing that earlier therapy in younger patients significantly delayed dialysis by 13 years compared to later or no therapy in older siblings. Therapy significantly improved life expectancy beyond the median age of 55 years of the no-treatment cohort. Thus, Alport syndrome is treatable with angiotensin-converting enzyme inhibition to delay renal failure and therapy improves life expectancy in a time-dependent manner. This supports the need for early diagnosis and early nephroprotective therapy in oligosymptomatic patients.

Autosomal recessive polycystic kidney disease (ARPKD) is an infantile form of PKD characterized by fusiform dilation of collecting ducts and congenital hepatic fibrosis. The ARPKD gene, PKHD1, is large (approximately 470 kb; 67 exons) with a 12222 bp longest open reading frame, although multiple different splice forms may be generated. The predicted full-length ARPKD protein, fibrocystin, is membrane bound with 4074 amino acids (447 kDa molecular weight). To characterize the pattern of fibrocystin expression we have generated four monoclonal antibodies (mAb) to the cytoplasmic tail of the protein. Western analysis of human kidney membrane protein showed an identical pattern with each mAb; a strongly expressing large product (>450 kDa), consistent with the predicted protein size, and a weaker approximately 220 kDa band. The same large product was detected in rat and mouse kidney with lower level expression in liver. To further show that these mAbs recognize fibrocystin, tissue from ARPKD patients was analyzed and no fibrocystin products were detected. Immunohistochemical analysis of the developing kidney showed expression in the branching ureteric bud and collecting ducts, expression that persisted into adulthood. Biliary duct staining was found in the liver, plus staining in the pancreas and developing testis. Immunofluorescence analysis of MDCK cells showed a major site of expression in the primary cilia. Recent studies have associated the disease protein in various human and animal forms of PKD with cilia. The localization of fibrocystin to cilia further strengthens that correlation and indicates that the primary defect in ARPKD may be linked to ciliary dysfunction.

Recently, the European Medicines Agency approved the use of the vasopressin V2 receptor antagonist tolvaptan to slow the progression of cyst development and renal insufficiency of autosomal dominant polycystic kidney disease (ADPKD) in adult patients with chronic kidney disease stages 1–3 at initiation of treatment with evidence of rapidly progressing disease. In this paper, on behalf of the ERA-EDTA Working Groups of Inherited Kidney Disorders and European Renal Best Practice, we aim to provide guidance for making the decision as to which ADPKD patients to treat with tolvaptan. The present position statement includes a series of recommendations resulting in a hierarchical decision algorithm that encompasses a sequence of risk-factor assessments in a descending order of reliability. By examining the best-validated markers first, we aim to identify ADPKD patients who have documented rapid disease progression or are likely to have rapid disease progression. We believe that this procedure offers the best opportunity to select patients who are most likely to benefit from tolvaptan, thus improving the benefit-to-risk ratio and cost-effectiveness of this treatment. It is important to emphasize that the decision to initiate treatment requires the consideration of many factors besides eligibility, such as contraindications, potential adverse events, as well as patient motivation and lifestyle factors, and requires shared decision-making with the patient.

SummaryBackground and objectives The increasing number of podocyte-expressed genes implicated in steroid-resistant nephrotic syndrome (SRNS), the phenotypic variability, and the uncharacterized relative frequency of mutations in these genes in pediatric and adult patients with SRNS complicate their routine genetic analysis. Our aim was to compile the clinical and genetic data of eight podocyte genes analyzed in 110 cases (125 patients) with SRNS (ranging from congenital to adult onset) to provide a genetic testing approach.Design, setting, participants, & measurements Mutation analysis was performed by sequencing the NPHS1, NPHS2, TRPC6, CD2AP, PLCE1, INF2, WT1 (exons 8 and 9), and ACTN4 (exons 1 to 10) genes. ResultsWe identified causing mutations in 34% (37/110) of SRNS patients, representing 67% (16/24) familial and 25% (21/86) sporadic cases. Mutations were detected in 100% of congenital-onset, 57% of infantileonset, 24 and 36% of early and late childhood-onset, 25% of adolescent-onset, and 14% of adult-onset patients. The most frequently mutated gene was NPHS1 in congenital onset and NPHS2 in the other groups. A partial remission was observed in 7 of 26 mutation carriers treated with immunosuppressive agents and/or angiotensin-converting enzyme inhibitors. Patients with NPHS1 mutations showed a faster progression to ESRD than patients with NPHS2 mutations. None of these mutation carriers relapsed after kidney transplantation. ConclusionsWe propose a genetic testing algorithm for SRNS based on the age at onset and the familial/ sporadic status. Mutation analysis of specific podocyte-genes has a clinical value in all age groups, especially in children.