Renal angiomyolipoma bleeding in a patient with TSC2/PKD1 contiguous gene syndrome after 17 years of renal replacement therapy

We report the case of a 32-year-old male diagnosed with TSC2/PKD1 contiguous gene syndrome, presenting with tuberous sclerosis (TS) and autosomal dominant polycystic kidney disease simultaneously. He progressed to end-stage renal disease and received a kidney transplant at the age of 12. The native kidneys presented angiomyolipomas (AML), which are common benign tumours in patients with TS. Seventeen years after transplantation, he presented with abdominal pain, anaemia and a retroperitoneal haematoma, the latter caused by renal AML bleeding. Selective embolisation was performed. Our patient could have benefited from the administration of mTOR inhibitors at transplant. This therapy is immunosuppressive and reduces the size of benign tumours in TS as well as the risk of rupture and bleeding. This patient did not receive mTOR inhibitors at the time of the transplant because the relationship between mTOR inhibitors and TS was unknown at that time. This case confirms the persistent risk of renal AML bleeding for both transplanted patients and patients on dialysis. As a result, we would recommend routine check-ups of native kidneys and nephrectomy assessment.

Treatment of Fabry's Disease with the Pharmacologic Chaperone Migalastat

BACKGROUND

Fabry's disease, an X-linked disorder of lysosomal α-galactosidase deficiency, leads to substrate accumulation in multiple organs. Migalastat, an oral pharmacologic chaperone, stabilizes specific mutant forms of α-galactosidase, increasing enzyme trafficking to lysosomes.

METHODS

The initial assay of mutant α-galactosidase forms that we used to categorize 67 patients with Fabry's disease for randomization to 6 months of double-blind migalastat or placebo (stage 1), followed by open-label migalastat from 6 to 12 months (stage 2) plus an additional year, had certain limitations. Before unblinding, a new, validated assay showed that 50 of the 67 participants had mutant α-galactosidase forms suitable for targeting by migalastat. The primary end point was the percentage of patients who had a response (≥50% reduction in the number of globotriaosylceramide inclusions per kidney interstitial capillary) at 6 months. We assessed safety along with disease substrates and renal, cardiovascular, and patient-reported outcomes.

RESULTS

The primary end-point analysis, involving patients with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy, did not show a significant treatment effect: 13 of 32 patients (41%) who received migalastat and 9 of 32 patients (28%) who received placebo had a response at 6 months (P=0.30). Among patients with suitable mutant α-galactosidase who received migalastat for up to 24 months, the annualized changes from baseline in the estimated glomerular filtration rate (GFR) and measured GFR were -0.30±0.66 and -1.51±1.33 ml per minute per 1.73 m(2) of body-surface area, respectively. The left-ventricular-mass index decreased significantly from baseline (-7.7 g per square meter; 95% confidence interval [CI], -15.4 to -0.01), particularly when left ventricular hypertrophy was present (-18.6 g per square meter; 95% CI, -38.2 to 1.0). The severity of diarrhea, reflux, and indigestion decreased.

CONCLUSIONS

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].).

Recommendations for the use of tolvaptan in autosomal dominant polycystic kidney disease: a position statement on behalf of the ERA-EDTA Working Groups on Inherited Kidney Disorders and European Renal Best Practice

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.

An update for atypical haemolytic uraemic syndrome: diagnosis and treatment. A consensus document

Haemolytic uraemic syndrome (HUS) is a clinical entity defined as the triad of nonimmune haemolytic anaemia, thrombocytopenia, and acute renal failure, in which the underlying lesions are mediated by systemic thrombotic microangiopathy (TMA). Different causes can induce the TMA process that characterizes HUS. In this document we consider atypical HUS (aHUS) a sub-type of HUS in which the TMA phenomena are the consequence of the endotelial damage in the microvasculature of the kidneys and other organs due to a disregulation of the activity of the complement system. In recent years, a variety of aHUs-related mutations have been identified in genes of the the complement system, which can explain approximately 60% of the aHUS cases, and a number of mutations and polymorphisms have been functionally characterized. These findings have stablished that aHUS is a consequence of the insufficient regulation of the activiation of the complement on cell surfaces, leading to endotelial damage mediated by C5 and the complement terminal pathway. Eculizumab is a monoclonal antibody that inhibits the activation of C5 and blocks the generation of the pro-inflammatory molecule C5a and the formation of the cell membrane attack complex. In prospective studies in patients with aHUS, the use of Eculizumab has shown a fast and sustained interruption of the TMA process and it has been associated with significative long-term improvements in renal function, the interruption of plasma therapy and important reductions in the need of dialysis. According to the existing literature and the accumulated clinical experience, the Spanish aHUS Group published a consensus document with recommendations for the treatment of aHUs (Nefrologia 2013;33[1]:27-45). In the current online version of this document, we update the aetiological classification of TMAs, the pathophysiology of aHUS, its differential diagnosis and its therapeutic management.

Autosomal-dominant polycystic kidney disease (ADPKD): executive summary from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Autosomal-dominant polycystic kidney disease (ADPKD) affects up to 12 million individuals and is the fourth 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 Kidney Disease: Improving Global Outcomes Controversies Conference on ADPKD brought together a panel of multidisciplinary 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 review.

Insight into response to mTOR inhibition when PKD1 and TSC2 are mutated

Background

Mutations in TSC1 or TSC2 cause the tuberous sclerosis complex (TSC), while mutations in PKD1 or PKD2 cause autosomal dominant polycystic kidney disease (ADPKD). PKD1 lays immediately adjacent to TSC2 and deletions involving both genes, the PKD1/TSC2 contiguous gene syndrome (CGS), are characterized by severe ADPKD, plus TSC. mTOR inhibitors have proven effective in reducing angiomyolipoma (AML) in TSC and total kidney volume in ADPKD but without a positive effect on renal function.

Methods and results

We describe a patient with independent truncating PKD1 and TSC2 mutations who has the expected phenotype for both diseases independently instead of the severe one described in PKD1/TSC2-CGS. Treatment with mTOR inhibitors reduced the AML and kidney volume for 2 years but thereafter they resumed growth; no positive effect on renal function was seen throughout. This is the first case addressing the response to mTOR treatment when independent truncating mutations in PKD1 and TSC2 are present.

Conclusions

This case reveals that although PKD1 and TSC2 are adjacent genes and there is likely cross-talk between the PKD1 and TSC2 signalling pathways regulating mTOR, having independent TSC2 and PKD1 mutations can give rise to a milder kidney phenotype than is typical in PKD1/TSC2-CGS cases. A short-term beneficial effect of mTOR inhibition on AML and total kidney volume was not reflected in improved renal function.

Cystinosis in adult and adolescent patients: Recommendations for the comprehensive care of cystinosis

INTRODUCTION

Cystinosis is a rare lysosomal systemic disease that mainly affects the kidney and the eye. Patients with cystinosis begin renal replacement therapy during the first decade of life in absence of treatment. Prognosis of cystinosis depends on early diagnosis, and prompt starting and good compliance with cysteamine treatment. Kidney disease progression, extra-renal complications and shorter life expectancy are more pronounced in those patients that do not follow treatment. The objective of this work was to elaborate recommendations for the comprehensive care of cystinosis and the facilitation of patient transition from paediatric to adult treatment, based on clinical experience. The goal is to reduce the impact of the disease, and to improve patient quality of life and prognosis.

METHODS

Bibliographic research and consensus meetings among a multidisciplinary professional team of experts in the clinical practice, with cystinotic patients (T-CiS.bcn group) from 5 hospitals located in Barcelona.

RESULTS

This document gathers specific recommendations for diagnosis, treatment and multidisciplinary follow-up of cystinotic patients in the following areas: nephrology, dialysis,renal transplant, ophthalmology, endocrinology, neurology, laboratory, genetic counselling,nursing and pharmacy.

CONCLUSIONS

A reference document for the comprehensive care of cystinosis represents a support tool for health professionals who take care of these patients. It is based on the following main pillars: (a) a multi-disciplinary approach, (b) appropriate disease monitoring and control of intracellular cystine levels in leukocytes, (c) the importance of adherence to treatment with cysteamine, and (d) the promotion of patient self-care by means of disease education programmes. All these recommendations will lead us, in a second phase, to create a coordinated transition model between paediatric and adult care services which will contemplate the specific needs of cystinosis.

Targeted next-generation sequencing in steroid-resistant nephrotic syndrome: mutations in multiple glomerular genes may influence disease severity

Genetic diagnosis of steroid-resistant nephrotic syndrome (SRNS) using Sanger sequencing is complicated by the high genetic heterogeneity and phenotypic variability of this disease. We aimed to improve the genetic diagnosis of SRNS by simultaneously sequencing 26 glomerular genes using massive parallel sequencing and to study whether mutations in multiple genes increase disease severity. High-throughput mutation analysis was performed in 50 SRNS and/or focal segmental glomerulosclerosis (FSGS) patients, a validation cohort of 25 patients with known pathogenic mutations, and a discovery cohort of 25 uncharacterized patients with probable genetic etiology. In the validation cohort, we identified the 42 previously known pathogenic mutations across NPHS1, NPHS2, WT1, TRPC6, and INF2 genes. In the discovery cohort, disease-causing mutations in SRNS/FSGS genes were found in nine patients. We detected three patients with mutations in an SRNS/FSGS gene and COL4A3. Two of them were familial cases and presented a more severe phenotype than family members with mutation in only one gene. In conclusion, our results show that massive parallel sequencing is feasible and robust for genetic diagnosis of SRNS/FSGS. Our results indicate that patients carrying mutations in an SRNS/FSGS gene and also in COL4A3 gene have increased disease severity.

Spanish guidelines for the management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent cause of genetic renal disease and accounts for 6-10% of patients on renal replacement therapy (RRT). Very few prospective, randomized trials or clinical studies address the diagnosis and management of this relatively frequent disorder. No clinical guidelines are available to date. This is a consensus statement presenting the recommendations of the Spanish Working Group on Inherited Kidney Diseases, which were agreed to following a literature search and discussions. Levels of evidence found were C and D according to the Centre for Evidence-Based Medicine (University of Oxford). The recommendations relate to, among other topics, the use of imaging and genetic diagnosis, management of hypertension, pain, cyst infections and bleeding, extra-renal involvement including polycystic liver disease and cranial aneurysms, management of chronic kidney disease (CKD) and RRT and management of children with ADPKD. Recommendations on specific ADPKD therapies are not provided since no drug has regulatory approval for this indication.

Building a network of ADPKD reference centres across Europe: the EuroCYST initiative

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic inherited kidney disease, affecting an estimated 600 000 individuals in Europe. The disease is characterized by age-dependent development of a multiple cysts in the kidneys, ultimately leading to end-stage renal failure and the need of renal replacement therapy in the majority of patients, typically by the fifth or sixth decade of life. The variable disease course, even within the same family, remains largely unexplained. Similarly, assessing disease severity and prognosis in an individual with ADPKD remains difficult. Epidemiological studies are limited due to the fragmentation of ADPKD research in Europe.

METHODS

The EuroCYST initiative aims: (i) to harmonize and develop common standards for ADPKD research by starting a collaborative effort to build a network of ADPKD reference centres across Europe and (ii) to establish a multicentric observational cohort of ADPKD patients. This cohort will be used to study factors influencing the rate of disease progression, disease modifiers, disease stage-specific morbidity and mortality, health economic issues and to identify predictive disease progression markers. Overall, 1100 patients will be enrolled in 14 study sites across Europe. Patients will be prospectively followed for at least 3 years. Eligible patients will not have participated in a pharmaceutical clinical trial 1 year before enrollment, have clinically proven ADPKD, an estimated glomerular filtration rate (eGFR) of 30 mL/min/1.73 m(2) and above, and be able to provide written informed consent. The baseline visit will include a physical examination and collection of blood, urine and DNA for biomarker and genetic studies. In addition, all participants will be asked to complete questionnaires detailing self-reported health status, quality of life, socioeconomic status, health-care use and reproductive planning. All subjects will undergo annual follow-up. A magnetic resonance imaging (MRI) scan will be carried out at baseline, and patients are encouraged to undergo a second MRI at 3-year follow-up for qualitative and quantitative kidney and liver assessments.

CONCLUSIONS

The ADPKD reference centre network across Europe and the observational cohort study will enable European ADPKD researchers to gain insights into the natural history, heterogeneity and associated complications of the disease as well as how it affects the lives of patients across Europe.

DNA variant databases improve test accuracy and phenotype prediction in Alport syndrome

X-linked Alport syndrome is a form of progressive renal failure caused by pathogenic variants in the COL4A5 gene. More than 700 variants have been described and a further 400 are estimated to be known to individual laboratories but are unpublished. The major genetic testing laboratories for X-linked Alport syndrome worldwide have established a Web-based database for published and unpublished COL4A5 variants ( https://grenada.lumc.nl/LOVD2/COL4A/home.php?select_db=COL4A5 ). This conforms with the recommendations of the Human Variome Project: it uses the Leiden Open Variation Database (LOVD) format, describes variants according to the human reference sequence with standardized nomenclature, indicates likely pathogenicity and associated clinical features, and credits the submitting laboratory. The database includes non-pathogenic and recurrent variants, and is linked to another COL4A5 mutation database and relevant bioinformatics sites. Access is free. Increasing the number of COL4A5 variants in the public domain helps patients, diagnostic laboratories, clinicians, and researchers. The database improves the accuracy and efficiency of genetic testing because its variants are already categorized for pathogenicity. The description of further COL4A5 variants and clinical associations will improve our ability to predict phenotype and our understanding of collagen IV biochemistry. The database for X-linked Alport syndrome represents a model for databases in other inherited renal diseases.

Autosomal dominant policystic kidney disease, more than a renal disease

Autosomal dominant polycystic kidney disease (ADPKD) is a systemic disorder mainly involving the kidney. It affects one in 400-1000 live births. Early hypertension and progressive renal failure due to massive enlargement of cysts and fibrosis are hallmarks of the disease. ADPKD accounts for ~5-10% of cases requiring renal replacement therapy. But not only the kidneys are affected in ADPKD: cysts also occur in other organs such as the liver, pancreas, arachnoid membrane and seminal vesicles. Non-cystic manifestations of the diseases are intracranial aneurysms, hernias and valvular abnormalities. Complications in ADPKD usually result from kidney involvement and include cyst bleeding and cyst infection. However, serious extrarenal features such as subarachnoid haemorrhage can also occur. There is no specific treatment for ADPKD currently, but many molecules targeting up- or downregulated molecules in the renal epithelial cells are being tested. A clinical trial using tolvaptan (a vasopressin receptor antagonist) has demonstrated efficacy, while mTOR inhibitors have shown no positive effect in ADPKD. ACEIs and ARBs are the drugs of choice for treating hypertension in ADPKD. Until a specific therapy becomes available, early treatment of hypertension and lifestyle changes are encouraged.

Diagnosis of autosomal dominant polycystic kidney disease using efficient PKD1 and PKD2 targeted next-generation sequencing

Molecular diagnostics of autosomal dominant polycystic kidney disease (ADPKD) relies on mutation screening of PKD1 and PKD2, which is complicated by extensive allelic heterogeneity and the presence of six highly homologous sequences of PKD1. To date, specific sequencing of PKD1 requires laborious long-range amplifications. The high cost and long turnaround time of PKD1 and PKD2 mutation analysis using conventional techniques limits its widespread application in clinical settings. We performed targeted next-generation sequencing (NGS) of PKD1 and PKD2. Pooled barcoded DNA patient libraries were enriched by in-solution hybridization with PKD1 and PKD2 capture probes. Bioinformatics analysis was performed using an in-house developed pipeline. We validated the assay in a cohort of 36 patients with previously known PKD1 and PKD2 mutations and five control individuals. Then, we used the same assay and bioinformatics analysis in a discovery cohort of 12 uncharacterized patients. We detected 35 out of 36 known definitely, highly likely, and likely pathogenic mutations in the validation cohort, including two large deletions. In the discovery cohort, we detected 11 different pathogenic mutations in 10 out of 12 patients. This study demonstrates that laborious long-range PCRs of the repeated PKD1 region can be avoided by in-solution enrichment of PKD1 and PKD2 and NGS. This strategy significantly reduces the cost and time for simultaneous PKD1 and PKD2 sequence analysis, facilitating routine genetic diagnostics of ADPKD.

Cost-effective PKHD1 genetic testing for autosomal recessive polycystic kidney disease

BACKGROUND

Genetic diagnosis of autosomal recessive polycystic kidney disease (ARPKD) is challenging due to the length and allelic heterogeneity of the PKHD1 gene. Mutations appear to be clustered at specific exons, depending on the geographic origin of the patient. We aimed to identify the PKHD1 exons most likely mutated in Spanish ARPKD patients.

METHODS

Mutation analysis was performed in 50 ARPKD probands and nine ARPKD-suspicious patients by sequencing PKHD1 exons arranged by their reported mutation frequency. Haplotypes containing the most frequent mutations were analyzed. Other PKD genes (HNF1B, PKD1, PKD2) were sequenced in PKHD1-negative cases.

RESULTS

Thirty-six different mutations (concentrated in 24 PKHD1 exons) were detected, giving a mutation detection rate of 86%. The screening of five exons (58, 32, 34, 36, 37) yielded a 54% chance of detecting one mutation; the screening of nine additional exons (3, 9, 39, 61, 5, 22, 26, 41, 57) increased the chance to 76%. The c.9689delA mutation was present in 17 (34%) patients, all of whom shared the same haplotype. Two HNF1B mutations and one PKD1 variant were detected in negative cases.

CONCLUSIONS

Establishing a PKHD1 exon mutation profile in a specific population and starting the analysis with the most likely mutated exons might significantly enhance the efficacy of genetic testing in ARPKD. Analysis of other PKD genes might be considered, especially in suspicious cases.