Severe parental phenotype associates with hypertension in children with ADPKD.

BACKGROUND: Early detection of hypertension in children with autosomal polycystic kidney disease (ADPKD) may be beneficial, but screening children at risk of ADPKD remains controversial. We investigated determinants of hypertension in children with ADPKD to help identify a subgroup of children at risk of ADPKD for whom screening for the disease and/or its complications would be more relevant. METHODS: In a retrospective study including consecutive children with ADPKD aged 5-18 years and followed at Saint-Luc Hospital Brussels between 2006 and 2020, we investigated the potential association between genotype, clinical characteristics and parental phenotype, and presence of hypertension. Hypertension was defined as blood pressure > P95 during 24-h ambulatory monitoring or anti-hypertensive therapy use. Parental phenotype was considered severe based on age at kidney failure, Mayo Clinic Imaging Classification and rate of eGFR decline. RESULTS: The study enrolled 55 children with ADPKD (mean age 9.9 ± 2.2 years, 45% male), including 44 with a PKD1 mutation and 5 with no mutation identified. Nine (16%) children had hypertension. Hypertension in children was associated with parental phenotype severity (8/27 (30%) children with severe parental phenotype vs. 1/23 (4%) children with non-severe parental phenotype (p = 0.03)) and height-adjusted bilateral nephromegaly (6/9 (67%) children with bilateral nephromegaly vs. 3/44 (7%) children without bilateral nephromegaly (p < 0.001)). CONCLUSIONS: Severe parental phenotype is associated with higher prevalence of hypertension in children with ADPKD. Hence, children of parents with severe ADPKD phenotype may be those who will most benefit from screening of the disease and/or yearly BP measures. A higher resolution version of the Graphical abstract is available as Supplementary information.

Illness-related parental stress and quality of life in children with kidney diseases.

BACKGROUND: This cross-sectional study investigated quality of life (QoL) and illness-related parental stress in children with kidney diseases by (1) comparing mean levels of these two variables between several kidney disease categories; (2) exploring correlations between QoL and parental stress; and (3) describing which disease category reports lowest QoL and highest parental stress. METHODS: We included 295 patients with a kidney disease (0-18 years) and their parents, followed at 6 reference centers for pediatric nephrology. Children's QoL was assessed by the PedsQL™ 4.0 Generic Core Scales, and illness-related stress by the Pediatric Inventory for Parents. All patients were divided into 5 kidney disease categories according to the multidisciplinary care program criteria prescribed by the Belgian authorities: (1) structural kidney diseases, (2) tubulopathies and metabolic diseases, (3) nephrotic syndrome, (4) acquired diseases with proteinuria and hypertension, and (5) kidney transplantation. RESULTS: Child self-reports showed no differences in QoL between kidney disease categories, in contrast to parent proxy reports. Parents of transplant patients reported lower QoL in their child and more parental stress compared with the 4 non-transplant categories. QoL and parental stress were negatively correlated. Lowest QoL and highest parental stress scores were mainly found in transplant patients. CONCLUSIONS: This study showed lower QoL and higher parental stress in pediatric transplant patients compared with non-transplants, based on parent reports. Higher parental stress is associated with worse QoL in the child. These results highlight the importance of multidisciplinary care for children with kidney diseases, with special attention to transplant patients and their parents. A higher resolution version of the Graphical abstract is available as Supplementary information.

mTOR-Activating Mutations in RRAGD Are Causative for Kidney Tubulopathy and Cardiomyopathy.

BACKGROUND: Over the last decade, advances in genetic techniques have resulted in the identification of rare hereditary disorders of renal magnesium and salt handling. Nevertheless, approximately 20% of all patients with tubulopathy lack a genetic diagnosis. METHODS: We performed whole-exome and -genome sequencing of a patient cohort with a novel, inherited, salt-losing tubulopathy; hypomagnesemia; and dilated cardiomyopathy. We also conducted subsequent in vitro functional analyses of identified variants of RRAGD, a gene that encodes a small Rag guanosine triphosphatase (GTPase). RESULTS: In eight children from unrelated families with a tubulopathy characterized by hypomagnesemia, hypokalemia, salt wasting, and nephrocalcinosis, we identified heterozygous missense variants in RRAGD that mostly occurred de novo. Six of these patients also had dilated cardiomyopathy and three underwent heart transplantation. We identified a heterozygous variant in RRAGD that segregated with the phenotype in eight members of a large family with similar kidney manifestations. The GTPase RagD, encoded by RRAGD, plays a role in mediating amino acid signaling to the mechanistic target of rapamycin complex 1 (mTORC1). RagD expression along the mammalian nephron included the thick ascending limb and the distal convoluted tubule. The identified RRAGD variants were shown to induce a constitutive activation of mTOR signaling in vitro. CONCLUSIONS: Our findings establish a novel disease, which we call autosomal dominant kidney hypomagnesemia (ADKH-RRAGD), that combines an electrolyte-losing tubulopathy and dilated cardiomyopathy. The condition is caused by variants in the RRAGD gene, which encodes Rag GTPase D; these variants lead to an activation of mTOR signaling, suggesting a critical role of Rag GTPase D for renal electrolyte handling and cardiac function.

Defects in KCNJ16 Cause a Novel Tubulopathy with Hypokalemia, Salt Wasting, Disturbed Acid-Base Homeostasis, and Sensorineural Deafness.

BACKGROUND: The transepithelial transport of electrolytes, solutes, and water in the kidney is a well-orchestrated process involving numerous membrane transport systems. Basolateral potassium channels in tubular cells not only mediate potassium recycling for proper Na+,K+-ATPase function but are also involved in potassium and pH sensing. Genetic defects in KCNJ10 cause EAST/SeSAME syndrome, characterized by renal salt wasting with hypokalemic alkalosis associated with epilepsy, ataxia, and sensorineural deafness. METHODS: A candidate gene approach and whole-exome sequencing determined the underlying genetic defect in eight patients with a novel disease phenotype comprising a hypokalemic tubulopathy with renal salt wasting, disturbed acid-base homeostasis, and sensorineural deafness. Electrophysiologic studies and surface expression experiments investigated the functional consequences of newly identified gene variants. RESULTS: We identified mutations in the KCNJ16 gene encoding KCNJ16, which along with KCNJ15 and KCNJ10, constitutes the major basolateral potassium channel of the proximal and distal tubules, respectively. Coexpression of mutant KCNJ16 together with KCNJ15 or KCNJ10 in Xenopus oocytes significantly reduced currents. CONCLUSIONS: Biallelic variants in KCNJ16 were identified in patients with a novel disease phenotype comprising a variable proximal and distal tubulopathy associated with deafness. Variants affect the function of heteromeric potassium channels, disturbing proximal tubular bicarbonate handling as well as distal tubular salt reabsorption.

Dietary fibre intake is low in paediatric chronic kidney disease patients but its impact on levels of gut-derived uraemic toxins remains uncertain.

BACKGROUND: Chronic kidney disease (CKD) in children is a pro-inflammatory condition leading to a high morbidity and mortality. Accumulation of organic metabolic waste products, coined as uraemic toxins, parallels kidney function decline. Several of these uraemic toxins are protein-bound (PBUT) and gut-derived. Gut dysbiosis is a hallmark of CKD, resulting in a state of increased proteolytic fermentation that might be counteracted by dietary fibre. Data on fibre intake in children with CKD are lacking. We aimed to assess dietary fibre intake in a paediatric CKD cohort and define its relationship with PBUT concentrations. METHODS: In this multi-centre, cross-sectional observational study, 61 non-dialysis CKD patients (9 ± 5 years) were included. Dietary fibre intake was assessed through the use of 24-h recalls or 3-day food records and coupled to total and free levels of 4 PBUTs (indoxyl sulfate (IxS), p-cresyl sulfate (pCS), p-cresyl glucuronide (pCG) and indole acetic acid (IAA). RESULTS: In general, fibre intake was low, especially in advanced CKD: 10 ± 6 g/day/BSA in CKD 4-5 versus 14 ± 7 in CKD 1-3 (p = 0.017). Lower concentrations of both total (p = 0.036) and free (p = 0.036) pCG were observed in the group with highest fibre intake, independent of kidney function. CONCLUSIONS: Fibre intake in paediatric CKD is low and is even worse in advanced CKD stages. Current dietary fibre recommendations for healthy children are not being achieved. Dietary management of CKD is complex in which too restrictive diets carry the risk of nutritional deficiencies. The relation of fibre intake with PBUTs remains unclear and needs further investigation. Graphical abstract.

Epstein-Barr Virus-associated Pulmonary Tumor: A Pediatric Case and Discussion of the Literature.

Epstein-Barr virus-associated smooth pulmonary tumor is a rare condition that mostly affects immunosuppressed patients. This case describes a young boy with a history of kidney transplantation who presented recurrent pneumonia. Multiple endobronchial soft tissue tumors affecting both right and left bronchial tree were found and partially removed by bronchoscopy. Immunohistologic analysis demonstrated Epstein-Barr virus-associated smooth pulmonary tumor. Immunosuppressive therapy was changed from tacrolimus to sirolimus. A few months later, new right upper lobe and inferior left lobe tumors were found. Recurrent left lower lobe pneumonia prompted lobectomy. In the present case, complete resection and change of immunosuppressive treatment were effective.

Typical or Atypical Hemolytic Uremic Syndrome and the Use of Eculizumab: 4 Illustrative Cases.

Typical hemolytic uremic syndrome (HUS) in children is caused mostly by Escherichia coli 0157:H7 in our country. Atypical HUS (aHUS) causes include Streptococcus pneumoniae, methyl malonic aciduria, deficiency of ADAMST 13, and genetic or acquired disorder of the complement. Treatment of HUS relies on supportive measures while treatment of aHUS includes plasmapheresis and specific treatments. Recently, eculizumab has been proposed for the treatment of aHUS and many clinicians now believe that eculizumab should be the first-line standard of care. The purpose of this article is to illustrate the difficulties in the diagnostic process of HUS and therefore the subsequent problem to promptly choose the appropriate treatment. To date, workup of HUS continues to take many days leaving the clinicians with a choice between several therapeutic options. With the emergence of eculizumab, it becomes crucial to find faster diagnostic tools and to adapt HUS treatment protocols. We reported here clinical cases where eculizumab use was probably not appropriate once the correct diagnosis of typical HUS was made and cases where it would have been useful because of the late diagnosis of aHUS.

Simultaneous sequencing of 37 genes identified causative mutations in the majority of children with renal tubulopathies.

The clinical diagnosis of inherited renal tubulopathies can be challenging as they are rare and characterized by significant phenotypic variability. Advances in sequencing technologies facilitate the establishment of a molecular diagnosis. Therefore, we determined the diagnostic yield of a next generation sequencing panel assessing relevant disease genes in children followed through three national networks with a clinical diagnosis of a renal tubulopathy. DNA was amplified with a kit provided by the European Consortium for High-Throughput Research in Rare Kidney Diseases with nine multiplex PCR reactions. This kit produced 571 amplicons covering 37 genes associated with tubulopathies followed by massive parallel sequencing and bioinformatic interpretation. Identified mutations were confirmed by Sanger sequencing. Overall, 384 index patients and 16 siblings were assessed. Most common clinical diagnoses were 174 patients with Bartter/Gitelman syndrome and 76 with distal renal tubular acidosis. A total of 269 different variants were identified in 27 genes, of which 95 variants were considered likely, 136 definitely pathogenic and 100 had not been described at annotation. These mutations established a genetic diagnosis in 245 of the index patients. Genetic testing changed the clinical diagnosis in 16 cases and provided insights into the phenotypic spectrum of the respective disorders. Our results demonstrate a high diagnostic yield of genetic testing in children with a clinical diagnosis of a renal tubulopathy, consistent with a predominantly genetic etiology in known disease genes. Thus, genetic testing helped establish a definitive diagnosis in almost two-thirds of patients thereby informing prognosis, management and genetic counseling.

Accumulation of uraemic toxins is reflected only partially by estimated GFR in paediatric patients with chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) in childhood is characterised by the accumulation of uraemic toxins resulting in a multisystem disorder that has a negative impact on quality of life. Childhood CKD is predominantly defined by a decrease in glomerular filtration rate, estimated (eGFR) by a single serum measurement of endogenous biomarkers, e.g. creatinine. The objective of this study was to evaluate how accurately eGFR predicts the concentration of uraemic toxins in a paediatric CKD cohort. METHODS: In 65 children (10.8 [5.1; 14.7] years) with CKD (eGFR 44 [20; 64] mL/min/1.73 m2), serum concentrations were determined of small solutes (uric acid [UA], urea, symmetric dimethylarginine [SDMA], asymmetric dimethylarginine [ADMA]), middle molecules (ß2-microglobulin [ß2M], complement factor D [CfD]) and protein-bound solutes (p-cresylglucuronide [pCG], hippuric acid, indole acetic acid, indoxyl sulphate [IxS], p-cresylsulfate [pCS] and 3-carboxy-4-methyl-5-propyl-furanpropionic acid [CMPF]). Spearman's correlation coefficients (r) were calculated to correlate uraemic toxin concentrations with three different eGFR equations, based on either serum creatinine or ß2M. RESULTS: Updated Schwartz eGFR was correlated reasonably well with concentrations of creatinine (r = -0.98), urea (rs = -0.84), SDMA (r = -0.82) and middle molecules CfD and ß2M (both rs = -0.90). In contrast, poor correlation coefficients were found for CMPF (rs = -0.32), UA (rs = -0.45), ADMA (rs = -0.47) and pCG (rs = -0.48). The other toxins, all protein-bound, had rs between -0.75 and -0.57. Comparable correlations were found between the three evaluated eGFR equations and uraemic toxin concentrations. CONCLUSIONS: This study demonstrates that eGFR poorly predicts concentrations of protein-bound uraemic toxins, UA and ADMA in childhood CKD. Therefore, eGFR only partially reflects the complexity of the accumulation pattern of uraemic toxins in childhood CKD.

ANCA vasculitis in a patient with Alport syndrome: a difficult diagnosis but a treatable disease!

BACKGROUND: Alport syndrome and ANCA-associated vasculitis are both rare diseases. The co-existence of these two conditions has never been reported. There is no obvious pathogenic link between these two glomerular diseases. The management of this case highlights the importance of a systematic approach when investigating the unexpected unfavourable evolution of a known glomerulopathy. CASE PRESENTATION: A-17 year old caucasian boy with a genetically proven X-linked Alport syndrome presented with progressive dyspnea, fatigue and pallor. His blood tests showed a severe anemia (Hb 6.9 g/dl) with acute worsening of kidney function (serum creatinine, normal 9 months earlier, was now 3.6 mg/dl). Microscopic hematuria and proteinuria also worsened. He soon developed signs of alveolar hemorrhage. Serological tests showed the presence of perinuclear ANCA with anti MPO specificity. Kidney biopsy showed a necrotizing and crescentic glomerulonephritis. Pulses of methylprednisolone were given in combination with plasmapheresis. The patient further received 6 pulses of cyclophosphamide, followed by maintenance oral azathioprine. During the 15-months follow up he remained well with serum creatinine back to normal, and some residual proteinuria and hematuria ascribed to Alport syndrome. CONCLUSION: We report a young patient with the coexistence of Alport syndrome and ANCA associated vasculitis. Clinicians should be aware of the possibility of a second acquired disease in a patient with a known kidney disease, genetic in this case. This coexistence is very rare, but should be considered even if both diseases are rare, if the evolution is atypical for the single (known) primary disease. The diagnosis of the added vasculitis prompted in our case the initiation of immunosuppressive drugs, with a favourable outcome.

Kidney Versus Combined Kidney and Liver Transplantation in Young People With Autosomal Recessive Polycystic Kidney Disease: Data From the European Society for Pediatric Nephrology/European Renal Association-European Dialysis and Transplant (ESPN/ERA-EDTA) Registry.

BACKGROUND: The choice for either kidney or combined liver-kidney transplantation in young people with kidney failure and liver fibrosis due to autosomal recessive polycystic kidney disease (ARPKD) can be challenging. We aimed to analyze the characteristics and outcomes of transplantation type in these children, adolescents, and young adults. STUDY DESIGN: Cohort study. SETTING & PARTICIPANTS: We derived data for children, adolescents, and young adults with ARPKD with either kidney or combined liver-kidney transplants for 1995 to 2012 from the ESPN/ERA-EDTA Registry, a European pediatric renal registry collecting data from 36 European countries. FACTOR: Liver transplantation. OUTCOMES & MEASUREMENTS: Transplantation and patient survival. RESULTS: 202 patients with ARPKD aged 19 years or younger underwent transplantation after a median of 0.4 (IQR, 0.0-1.4) years on dialysis therapy at a median age of 9.0 (IQR, 4.1-13.7) years. 32 (15.8%) underwent combined liver-kidney transplantation, 163 (80.7%) underwent kidney transplantation, and 7 (3.5%) were excluded because transplantation type was unknown. Age- and sex-adjusted 5-year patient survival posttransplantation was 95.5% (95% CI, 92.4%-98.8%) overall: 97.4% (95% CI, 94.9%-100.0%) for patients with kidney transplantation in contrast to 87.0% (95% CI, 75.8%-99.8%) with combined liver-kidney transplantation. The age- and sex-adjusted risk for death after combined liver-kidney transplantation was 6.7-fold (95% CI, 1.8- to 25.4-fold) greater than after kidney transplantation (P=0.005). Five-year death-censored kidney transplant survival following combined liver-kidney and kidney transplantation was similar (92.1% vs 85.9%; P=0.4). LIMITATIONS: No data for liver disease of kidney therapy recipients. CONCLUSIONS: Combined liver-kidney transplantation in ARPKD is associated with increased mortality compared to kidney transplantation in our large observational study and was not associated with improved 5-year kidney transplant survival. Long-term follow-up of both kidney and liver involvement are needed to better delineate the optimal transplantation strategy.

Children of non-Western origin with end-stage renal disease in the Netherlands, Belgium and a part of Germany have impaired health-related quality of life compared with Western children.

BACKGROUND: Many children with end-stage renal disease (ESRD) living in Western Europe are of non-Western European origin. They have unfavourable somatic outcomes compared with ESRD children of Western origin. In this study, we compared the Health-related Quality of Life (HRQoL) of both groups. METHODS: All children (5-18 years) with ESRD included in the RICH-Q project (Renal Insufficiency therapy in Children-Quality assessment and improvement) or their parents were asked to complete the generic version of the Paediatric Quality-of-Life Inventory 4.0 (PedsQL). RICH-Q comprises the Netherlands, Belgium and a part of Germany. Children were considered to be of non-Western origin if they or at least one parent was born outside Western-European countries. Impaired HRQoL for children with ESRD of Western or non-Western origin was defined as a PedsQL score less than fifth percentile for healthy Dutch children of Western or non-Western origin, respectively. RESULTS: Of the 259 eligible children, 230 agreed to participate. One hundred and seventy-four children responded (response rate 67%) and 55 (32%) were of non-Western origin. Overall, 31 (56%) of the ESRD children of non-Western origin, and 58 (49%) of Western origin had an impaired total HRQoL score. Total HRQoL scores of children with ESRD of Western origin and non-Western origin were comparable, but scores on emotional functioning and school functioning were lower in non-Western origin (P=0.004 and 0.01, respectively). The adjusted odds ratios (95% confidence interval) for ESRD children of non-Western origin to have impaired emotional functioning and school functioning, compared with Western origin, were 3.3(1.5-7.1) and 2.2(1.1-4.2), respectively. CONCLUSION: Children with ESRD of non-Western origin in three Western countries were found to be at risk for impaired HRQoL on emotional and school functioning. These children warrant special attention.

Monogenic Kidney Diseases in Kidney Transplantation.

Monogenic kidney diseases are involved in up to 15% of end-stage kidney diseases (ESKDs) in adults, and in 70 % of pediatric patients. When these disorders lead to kidney failure (KF), kidney transplantation (KT) is the preferred mode of replacement therapy. KT requires specific considerations depending on the nature of the genetic disorder, the potential oncological risk, the risk of recurrence in the graft, the possibility of specific complications of immunosuppression, and the issue of living donation. The availability of genetic testing should play an increasing role in the evaluation of patients or related living donor candidates before transplantation, relevant for the pretransplantation and posttransplantation management.

Indoxyl Sulfate Contributes to Impaired Height Velocity in (Pre)School Children.

Introduction: Growth failure is considered the most important clinical outcome parameter in childhood chronic kidney disease (CKD). Central to the pathophysiology of growth failure is the presence of a chronic proinflammatory state, presumed to be partly driven by the accumulation of uremic toxins. In this study, we assessed the association between uremic toxin concentrations and height velocity in a longitudinal multicentric prospective pediatric CKD cohort of (pre)school-aged children and children during pubertal stages. Methods: In a prospective, multicentric observational study, a selection of uremic toxin levels of children (aged 0-18 years) with CKD stage 1 to 5D was assessed every 3 months (maximum 2 years) along with clinical growth parameters. Linear mixed models with a random slope for age and a random intercept for child were fitted for height (in cm and SD scores [SDS]). A piecewise linear association between age and height was assumed. Results: Data analysis included data from 560 visits of 81 children (median age 9.4 years; 2/3 male). In (pre)school aged children (aged 2-12 years), a 10% increase in concurrent indoxyl sulfate (IxS, total) concentration resulted in an estimated mean height velocity decrease of 0.002 SDS/yr (P < 0.05), given that CKD stage, growth hormone (GH), bicarbonate concentration, and dietary protein intake were held constant. No significant association with height velocity was found in children during pubertal stages (aged >12 years). Conclusion: The present study demonstrated that, especially IxS contributes to a lower height velocity in (pre)school children, whereas we could not find a role for uremic toxins with height velocity during pubertal stages.

Policy variation in donor and recipient status in 11 pediatric renal transplantation centers.

BACKGROUND: Evidence-based guidelines for pediatric renal transplantation (Tx) are lacking. This may lead to unwanted treatment variations. We aimed to quantify the variation in treatment policies and its consequences in daily practice in 11 centers that provide renal Tx for children in three European countries. METHODS: We surveyed Tx policies in all ten centers in the Netherlands and Belgium and one center in Germany. We compared Tx policies with the therapies actually provided and with recommendations from available published guidelines and existing literature. Information on treatment policies was obtained by a questionnaire; information on care actually provided was registered prospectively from 2007 to 2011. The clinical guidelines were identified by searches of MEDLINE and websites of pediatric nephrology organizations. RESULTS: Between centers, we found discrepancies in policies on: the minimum accepted recipient weight (8-12 kg), the maximum living and deceased donor age (50-75 and 45-60 years, respectively). HLA-match policies varied between acceptation of all mismatches to at least 1A1B1DR match donor transplantations amounting to 49 % in the Netherlands versus 26 % in Belgium (p = 0.006). CONCLUSIONS: Management policies for renal Tx in children vary considerably between centers and nations. This has a direct impact on the delivered care, and by extrapolation, on health outcome.

Characterization, evolution and risk factors of diabetes and prediabetes in a pediatric cohort of renal and liver transplant recipients.

Background: Hyperglycemia (HG) and prediabetes are rarely sought in pediatric liver (LT) and renal (RT) transplantation, yet their presence indicates a high risk of diabetes and cardiovascular disease. The objectives of our DIABGRAFT study were to retrospectively (rDIABGRAFT) and longitudinally (pDIABGRAFT) characterize HG and (pre)diabetes in a cohort of children with LT or/and RT. Methods: We retrospectively analyzed risk factors of HG from 195 children with LT from 2012 to 2019 and twenty children with RT from 2005 to 2019 at Cliniques universitaires Saint-Luc. In addition, we prospectively followed four LT and four RT children to evaluate the evolution of their glucose metabolism. Results: Our rDIABGRAFT study showed that 25% and 35% of LT and RT children respectively presented transient HG and 20% of RT developed diabetes. The occurrence of HG was associated with the use of glucocorticoids and with acute events as graft rejection and infection. In our pDIABGRAFT cohort, biological markers of diabetes were in the normal range for HbA1C, fasting glucose and insulin levels. However, oral glucose tolerance test and glucose sensors showed insulin resistance, impaired glucose tolerance and HG in the post-prandial afternoon period. Conclusion: Our study shows that children with LT and RT were more at risk of developing HG when glucocorticoids were required and that HbA1C and fasting glucose lack sensitivity for early detection of glucose intolerance. Also, measurement of glycemia immediately after the transplantation and in postprandial period is key to detect dysglycemia since insulin resistance prevailed in our cohort. ClinicalTrialsgov ID: NCT05464043.

Epidemiology, Outcomes, and Complement Gene Variants in Secondary Thrombotic Microangiopathies.

BACKGROUND: The identification of complement defects as major drivers of primary atypical hemolytic uremic syndrome (HUS) has transformed the landscape of thrombotic microangiopathies (TMAs), leading to the development of targeted therapies and better patient outcomes. By contrast, little is known about the presentation, genetics, and outcomes of TMA associated with specific diseases or conditions, also referred to as secondary TMA. METHODS: In this study, we assessed the relative incidence, clinical and genetic spectra, and long-term outcomes of secondary TMA versus other TMAs in consecutive patients hospitalized with a first episode of TMA from 2009 to 2019 at two European reference centers. RESULTS: During the study period, 336 patients were hospitalized with a first episode of TMA. Etiologies included atypical HUS in 49 patients (15%), thrombotic thrombocytopenic purpura (TTP) in 29 (9%), shigatoxin-associated HUS in 70 (21%), and secondary TMA in 188 (56%). The main causes of secondary TMA were hematopoietic stem-cell transplantation ( n =56, 30%), solid-organ transplantation ( n =44, 23%), and malignant hypertension ( n =25, 13%). Rare variants in complement genes were identified in 32 of 49 patients (65%) with atypical HUS and eight of 64 patients (13%) with secondary TMA; pathogenic or likely pathogenic variants were found in 24 of 49 (49%) and two of 64 (3%) of them, respectively ( P < 0.001). After a median follow-up of 1157 days, death or kidney failure occurred in 14 (29%), eight (28%), five (7%), and 121 (64%) patients with atypical HUS, TTP, shigatoxin-associated HUS, and secondary TMA, respectively. Unadjusted and adjusted Cox regressions showed that patients with secondary TMA had the highest risk of death or kidney failure (unadjusted hazard ratio [HR], 3.35; 95% confidence interval [CI], 1.85 to 6.07; P < 0.001; adjusted HR, 4.11; 95% CI, 2.00 to 8.46; P < 0.001; considering atypical HUS as reference). CONCLUSIONS: Secondary TMAs represent the main cause of TMA and are independently associated with a high risk of death and progression to kidney failure.

Autosomal dominant polycystic kidney disease is associated with central and nephrogenic defects in osmoregulation.

Autosomal dominant polycystic kidney disease (ADPKD) is associated with a urine-concentrating defect attributed to renal cystic changes. As PKD genes are expressed in the brain, altered central release of arginine vasopressin could also play a role. In order to help determine this we measured central and nephrogenic components of osmoregulation in 10 adults and 10 children with ADPKD, all with normal renal function, and compared them to 20 age- and gender-matched controls. Overnight water deprivation caused a lower rise in urine osmolality in the patients with ADPKD than controls, reflecting an impaired release of vasopressin and a peripheral defect in the patients. The reactivity of plasma vasopressin to water deprivation, as found in controls, was blunted in the patients with the latter showing lower urine osmolality for the same range of plasma vasopressin. The maximal urine osmolality correlated negatively with total kidney volume. Defective osmoregulation was confirmed in the children with ADPKD but was unrelated to number of renal cysts or kidney size. Thus, patients with ADPKD have an early defect in osmoregulation, with a blunted release of arginine vasopressin. This reflects expression of polycystins in hypothalamic nuclei that synthesize vasopressin, and this should be considered when evaluating treatments targeting the vasopressin pathway in ADPKD.

Important differences in management policies for children with end-stage renal disease in the Netherlands and Belgium--report from the RICH-Q study.

BACKGROUND: The low prevalence of childhood end-stage renal disease and the small centre sizes have been a barrier for clinical studies and the development of evidence-based guidelines for chronic renal replacement therapy (cRRT) in children. Few data exist on the quality of care for these patients and the applicability of existing guidelines. The aim of this study is to quantify variation in treatment policies and actually delivered care in nine centres that deliver cRRT for children. METHODS: We surveyed treatment policies in all nine centres in the Netherlands and Belgium and compared them with the actually provided therapies and with recommendations from available guidelines. Data on treatment policies were gathered by questionnaires; actually provided care and outcomes were registered prospectively from 2007 to 2010. RESULTS: Data on policies and actual patient care were obtained from all nine centres. We found relevant differences between centres in treatment policies on various topics, e.g. estimated glomerular filtration rate threshold as an indication for initiation of cRRT, preferred initial mode of cRRT, peritoneal dialysis catheter care, haemodialysis frequency and vascular access. Discrepancies were seen between stated treatment policies and actual performed therapies. For the majority of policies, no evidence-based guidelines are available. CONCLUSIONS: Health care disparities exist due to large and unwanted variation in treatment policies between hospitals providing cRRT for children. Delivered care does not live up to stated policies, for which clear and internationally accepted guidelines are lacking.