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Children with glomerular disease have unique risk factors for compromised bone health. Studies addressing skeletal complications in this population are lacking.This retrospective cohort study utilized data from PEDSnet, a national network of pediatric health systems with standardized electronic health record data for more than 6.5 million patients from 2009 to 2021. Incidence rates (per 10,000 person-years) of fracture, slipped capital femoral epiphysis (SCFE), and avascular necrosis/osteonecrosis (AVN) in 4598 children and young adults with glomerular disease were compared with those among 553,624 general pediatric patients using Poisson regression analysis. The glomerular disease cohort was identified using a published computable phenotype. Inclusion criteria for the general pediatric cohort were two or more primary care visits 1 year or more apart between 1 and 21 years of age, one visit or more every 18 months if followed3 years, and no chronic progressive conditions defined by the Pediatric Medical Complexity Algorithm. Fracture, SCFE, and AVN were identified using SNOMED-CT diagnosis codes; fracture required an associated x-ray or splinting/casting procedure within 48 hours.We found a higher risk of fracture for the glomerular disease cohort compared with the general pediatric cohort in girls only (incidence rate ratio [IRR], 1.6; 95% CI, 1.3 to 1.9). Hip/femur and vertebral fracture risk were increased in the glomerular disease cohort: adjusted IRR was 2.2 (95% CI, 1.3 to 3.7) and 5 (95% CI, 3.2 to 7.6), respectively. For SCFE, the adjusted IRR was 3.4 (95% CI, 1.9 to 5.9). For AVN, the adjusted IRR was 56.2 (95% CI, 40.7 to 77.5).Children and young adults with glomerular disease have significantly higher burden of skeletal complications than the general pediatric population.

Acute kidney injury (AKI) is common in lupus nephritis (LN) and a risk factor for development of chronic kidney disease. In adults with LN, AKI severity correlates with the incidence of kidney failure and patient survival. Data on AKI outcomes in children with LN, particularly those requiring kidney replacement therapy (KRT), are limited.A multicenter, retrospective cohort study was performed in children diagnosed between 2010 and 2019 with LN and AKI stage 3 treated with dialysis (AKI stage 3D). Descriptive statistics were used to characterize demographics, clinical data, and kidney biopsy findings; treatment data for LN were not included. Logistic regression was used to examine the association of these variables with kidney failure.Fifty-nine patients (mean age 14.3 years, 84.7% female) were identified. The most common KRT indications were fluid overload (86.4%) and elevated blood urea nitrogen/creatinine (74.6%). Mean follow-up duration was 3.9 ± 2.9 years. AKI recovery without progression to kidney failure occurred in 37.3% of patients. AKI recovery with later progression to kidney failure occurred in 25.4% of patients, and there was no kidney recovery from AKI in 35.6% of patients. Older age, severe ( 50%) tubular atrophy and interstitial fibrosis, and National Institutes of Health (NIH) chronicity index score 4 on kidney biopsy were associated with kidney failure.Children with LN and AKI stage 3D have a high long-term risk of kidney failure. Severe tubular atrophy and interstitial fibrosis at the time of AKI, but not AKI duration, are predictive of kidney disease progression. A higher resolution version of the Graphical abstract is available as Supplementary information.

IntroductionPlasma carboxypeptidase B2 (CPB2) is an enzyme that cleaves C-terminal amino acids from proteins, thereby regulating their activities. CPB2 has anti-inflammatory and anti-fibrinolytic properties and can therefore be protective or harmful in disease. We explored the impact of functional carboxypeptidase B2 gene (CPB2) polymorphisms on graft survival following kidney transplantation.MethodsWe performed a longitudinal cohort study to evaluate the association of functionalCPB2polymorphisms (rs2146881, rs3742264, rs1926447, rs3818477) and complement polymorphisms (rs2230199, rs17611) with long-term allograft survival in 1,271 kidney transplant pairs from the University Medical Center Groningen in The Netherlands.ResultsThe high-producingCPB2rs3742264 polymorphism in the donor was associated with a reduced risk of graft loss following kidney transplantation (hazard ratio, 0.71 for the A-allele; 95%-CI, 0.55–0.93;P=0.014). In fully adjusted models, the association between the CPB2 polymorphism in the donor and graft loss remained significant. The protective effect of the high-producingCPB2variant in the donor could be mitigated by the hazardous effect of gain-of-function complement polymorphisms. Additionally, we compiled a genetic risk score of the fourCPB2variants in the recipients and donors, which was independently associated with long-term allograft survival. Furthermore, this genetic risk score substantially improved risk prediction for graft loss beyond currently used clinical predictors.ConclusionKidney allografts from deceased donors possessing a high-producing CPB2 polymorphism are at a lower risk of graft loss after kidney transplantation. Furthermore, our findings suggest that CPB2 might have a protective effect on graft loss through its ability to inactivate complement anaphylatoxins.EssentialsCarboxypeptidase B2 (CPB2) is a metalloprotease with anti-fibrinolytic and anti-inflammatory properties.We investigated the impact ofCPB2polymorphisms on graft loss after kidney transplantation.The rs3742264-A SNP in the donor, linked to higher CPB2 levels, decreased the risk of graft loss.CPB2 could have a protective effect on graft survival by inactivating complement anaphylatoxins.

Introduction: C3 glomerulopathy (C3G) is a rare, progressive kidney disease resulting from dysregulation of the alternative pathway (AP) of complement. Biomarkers at baseline were investigated in patients with C3G who participated in two phase 2 studies with the factor D (FD) inhibitor, danicopan. Methods: Patients with biopsy-confirmed C3G, proteinuria ≥500 mg/day, and estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m2 were enrolled into two studies (NCT03369236 and NCT03459443). Biomarker analysis was performed for patients with C3G confirmed by central pathology laboratory re-evaluation. Complement and clinical biomarkers, biopsy composite score, and activity and chronicity indices were assessed at baseline and analyzed by pairwise Spearman correlation analysis. Results: Twenty-nine patients were included in the analysis (median [interquartile range] age: 24.0 [10.0] years). Systemic complement AP activation was evident by reduced median concentrations of C3 and C5, elevated sC5b-9, and normal C4, relative to reference ranges. C3 showed strong pairwise correlations with C5 and sC5b-9 (r = 0.80 and −0.73, respectively; p < 0.0001). Baseline Ba and FD concentrations were inversely correlated with eGFR (r = −0.83 and −0.87, respectively; p < 0.0001). Urinary concentrations of sC5b-9 were correlated with both plasma sC5b-9 and proteinuria (r = 0.69 and r = 0.83, respectively; p < 0.0001). Biopsy activity indices correlated strongly with biomarkers of systemic AP activation, including C3 (r = −0.76, p < 0.0001), whereas chronicity indices aligned more closely with eGFR (r = −0.57, p = 0.0021). Conclusion: Associations among complement biomarkers, kidney function, and kidney histology may add to the current understanding of C3G and assist with the characterization of patients with this heterogenous disease.

BACKGROUND AND OBJECTIVES: Performing adequately powered clinical trials in pediatric diseases, such as SLE, is challenging. Improved recruitment strategies are needed for identifying patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Electronic health record algorithms were developed and tested to identify children with SLE both with and without lupus nephritis. We used single-center electronic health record data to develop computable phenotypes composed of diagnosis, medication, procedure, and utilization codes. These were evaluated iteratively against a manually assembled database of patients with SLE. The highest-performing phenotypes were then evaluated across institutions in PEDSnet, a national health care systems network of >6.7 million children. Reviewers blinded to case status used standardized forms to review random samples of cases (n=350) and noncases (n=350). RESULTS: Final algorithms consisted of both utilization and diagnostic criteria. For both, utilization criteria included two or more in-person visits with nephrology or rheumatology and ≥60 days follow-up. SLE diagnostic criteria included absence of neonatal lupus, one or more hydroxychloroquine exposures, and either three or more qualifying diagnosis codes separated by ≥30 days or one or more diagnosis codes and one or more kidney biopsy procedure codes. Sensitivity was 100% (95% confidence interval [95% CI], 99 to 100), specificity was 92% (95% CI, 88 to 94), positive predictive value was 91% (95% CI, 87 to 94), and negative predictive value was 100% (95% CI, 99 to 100). Lupus nephritis diagnostic criteria included either three or more qualifying lupus nephritis diagnosis codes (or SLE codes on the same day as glomerular/kidney codes) separated by ≥30 days or one or more SLE diagnosis codes and one or more kidney biopsy procedure codes. Sensitivity was 90% (95% CI, 85 to 94), specificity was 93% (95% CI, 89 to 97), positive predictive value was 94% (95% CI, 89 to 97), and negative predictive value was 90% (95% CI, 84 to 94). Algorithms identified 1508 children with SLE at PEDSnet institutions (537 with lupus nephritis), 809 of whom were seen in the past 12 months. CONCLUSIONS: Electronic health record–based algorithms for SLE and lupus nephritis demonstrated excellent classification accuracy across PEDSnet institutions.

Introduction: C3 glomerulopathy (C3G) is an ultrarare, chronic and progressive nephropathy mediated by dysregulation of the alternative pathway of complement (AP), with poor prognosis and limited treatment options. Targeted inhibition of proximal AP through factor D (FD) blockade represents a rational treatment approach. We present two phase 2 proof-of-concept clinical studies of the orally active FD inhibitor danicopan in patients with C3G and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) (NCT03369236 and NCT03459443). Methods: A double-blind, placebo-controlled study in patients with C3G and a single-arm, open-label study in patients with C3G or IC-MPGN treated with danicopan are reported. The studies evaluated pharmacokinetic/pharmacodynamic (PK/PD), efficacy, and safety outcomes. The co-primary endpoints were change from baseline in composite biopsy score and the proportion of patients with a 30% reduction in proteinuria relative to baseline at 6 or 12 months. Results: Optimal systemic concentrations of danicopan were not achieved for complete and sustained inhibition of AP, although there was evidence that blockade of FD reduced AP activity shortly after drug administration. Consequently, limited clinical response was observed in key efficacy endpoints. While stable disease or improvement from baseline was seen in some patients, response was not consistent. The data confirmed the favorable safety profile of danicopan. Conclusion: While demonstrating a favorable safety profile, danicopan resulted in incomplete and inadequately sustained inhibition of AP, probably due to limitations in its PK/PD profile in C3G, leading to lack of efficacy. Complete and sustained AP inhibition is required for a clinical response in patients with C3G.

Background The rarity of pediatric glomerular disease makes it difficult to identify sufficient numbers of participants for clinical trials. This leaves limited data to guide improvements in care for these patients. Methods The authors developed and tested an electronic health record (EHR) algorithm to identify children with glomerular disease. We used EHR data from 231 patients with glomerular disorders at a single center to develop a computerized algorithm comprising diagnosis, kidney biopsy, and transplant procedure codes. The algorithm was tested using PEDSnet, a national network of eight children's hospitals with data on >6.5 million children. Patients with three or more nephrologist encounters (n=55,560) not meeting the computable phenotype definition of glomerular disease were defined as nonglomerular cases. A reviewer blinded to case status used a standardized form to review random samples of cases (n=800) and nonglomerular cases (n=798). Results The final algorithm consisted of two or more diagnosis codes from a qualifying list or one diagnosis code and a pretransplant biopsy. Performance characteristics among the population with three or more nephrology encounters were sensitivity, 96% (95% CI, 94% to 97%); specificity, 93% (95% CI, 91% to 94%); positive predictive value (PPV), 89% (95% CI, 86% to 91%); negative predictive value, 97% (95% CI, 96% to 98%); and area under the receiver operating characteristics curve, 94% (95% CI, 93% to 95%). Requiring that the sum of nephrotic syndrome diagnosis codes exceed that of glomerulonephritis codes identified children with nephrotic syndrome or biopsy-based minimal change nephropathy, FSGS, or membranous nephropathy, with 94% sensitivity and 92% PPV. The algorithm identified 6657 children with glomerular disease across PEDSnet, ≥50% of whom were seen within 18 months. Conclusions The authors developed an EHR-based algorithm and demonstrated that it had excellent classification accuracy across PEDSnet. This tool may enable faster identification of cohorts of pediatric patients with glomerular disease for observational or prospective studies.

BACKGROUND: Children who are critically ill with AKI suffer from high morbidity and mortality rates, and lack treatment options. Emerging evidence implicates the role of complement activation in AKI pathogenesis, which could potentially be treated with complement inhibitors. The purpose of this study is to evaluate the association between complement activation fragments and severity of AKI in children who are critically ill. METHODS: A biorepository of samples from children who are critically ill from a prior multisite study was leveraged to identify children with stage 3 AKI and matched to patients without AKI on the basis of PELOD-2 (illness severity) scores. Specimens were analyzed for plasma and urine complement activation fragments of factor B, C3a, C4a, and sC5b-9. The primary outcomes were MAKE30 and severe AKI rates. RESULTS: In total, 14 patients with stage 3 AKI (five requiring RRT) were matched to 14 patients without AKI. Urine factor Ba and plasma C4a levels increased stepwise as severity of AKI increased, from no AKI to stage 3 AKI, to stage 3 AKI with RRT need. Plasma C4a levels were independently associated with increased risk of MAKE30 outcomes (OR, 3.2; IQR, 1.1–8.9), and urine Ba (OR, 1.9; IQR, 1.1–3.1), plasma Bb (OR, 2.7; IQR, 1.1–6.8), C4a (OR, 13.0; IQR, 1.6–106.6), and C3a (OR, 3.3; IQR, 1.3–8.4) were independently associated with risk of severe stage 2–3 AKI on day 3 of admission. CONCLUSIONS: Multiple complement fragments increase as magnitude of AKI severity increases. Very high levels of urine Ba or plasma C4a may identify patients at risk for severe AKI, hemodialysis, and MAKE30 outcomes. The fragments may be useful as a functional biomarker of complement activation and may identify those patients to study complement inhibition to treat or prevent AKI in children who are critically ill. These findings suggest the need for further specific investigations of the role of complement activation in children who are critically ill and at risk of AKI.

Background and Aims C3 glomerulopathy (C3G) and immune complex membranoproliferative glomerulonephritis (IC-MPGN) are rare, progressive kidney diseases requiring a biopsy for definite diagnosis. Both C3G and IC-MPGN are attributed to complement dysregulation, with dysregulation of the alternative pathway established in C3G and implicated in IC-MPGN (alongside classical pathway activation by immune complexes). We describe the baseline biomarker and clinical characteristics of patients participating in two C3G/IC-MPGN phase II studies of the investigational, oral complement factor D (FD) inhibitor, danicopan (ALXN2040/ACH-4471). Method The first study (NCT03369236) was a double-blind, placebo-controlled, randomised, 6-month (+open label extension) trial of patients with biopsy-confirmed C3G of the native kidney treated with danicopan or placebo. The second study (NCT03459443) was a single-arm, open-label, 12-month (+extension) trial of patients with biopsy-confirmed C3G or IC-MPGN treated with danicopan. In both studies, all patients were to have proteinuria ≥500 mg/day and estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m2 (calculated by the Modification of Diet in Renal Disease equation for patients ≥18 years and the Schwartz equation for patients Results A total of 35 patients were included in this analysis (13 from study 1 and 22 from study 2). The majority of patients were male (9 [69%] in study 1, 12 [55%] in study 2), with mean (SD) ages at baseline of 25.2 (7.63) years in study 1 and 24.3 (9.90) years in study 2. Most patients had received prior angiotensin converting enzyme inhibitors/receptor blockers (12 [92%] in study 1, 19 [86%] in study 2), and/or immunosuppressants (10 [77%] in study 1, 12 [55%] in study 2). Baseline clinical and biomarker data are shown in Table 1. Baseline eGFR was moderately correlated with proteinuria (uPCR24, rs=-0.40 [p=0.022]); baseline uPCR24 was also moderately correlated with Ba (rs=0.42 [p=0.016]) and FD (rs=0.53 [p=0.002]). Ba and FD elevations showed strong correlations with lower eGFR (rs=-0.79 and -0.88, respectively [p Conclusion Data from two danicopan clinical studies in C3G patients show correlations with renal impairment and proteinuria were observed for some, but not all, complement biomarkers. Factor Ba and FD are strongly associated with eGFR, suggesting that these biomarkers cannot easily be used as markers of complement dysregulation or activity. Interpretation of changes in these complement proteins needs to include not only the nature of the complement dysregulation and influence of the complement therapeutic being tested, but also eGFR. Additional urinary biomarkers, biopsy findings, autoantibodies, and genetic variants are currently being analysed and findings from this study will contribute to a better understanding of C3G and IC-MPGN.

Atypical hemolytic uremic syndrome (aHUS) is a form of thrombotic microangiopathy mediated by dysregulation of the alternative complement pathway. Complement-amplifying conditions such as respiratory and gastrointestinal infections, pregnancy, malignancy, and systemic autoimmune diseases such as systemic lupus erythematosus have been associated with the clinical manifestation of aHUS. Inflammation of the gastrointestinal tract is a potent stimulus for complement activation, and we describe a series of three pediatric patients with aHUS and comorbidity of inflammatory bowel disease (IBD). In two of the three cases, the diagnosis of aHUS preceded the diagnosis of IBD, perhaps suggesting a mechanistic link between complement dysregulation and thrombotic microangiopathy in the gastrointestinal tract and the ensuing inflammatory changes of IBD.

Hemolytic uremic syndrome (HUS) is the clinical triad of thrombocytopenia, anemia, and acute kidney injury. Classically associated with enterocolitis from Shiga toxin-producing Escherichia coli, HUS is also associated with Streptococcus pneumoniae infections; genetic dysregulation of the alternative complement pathway or coagulation cascade; and, rarely, a hereditary disorder of cobalamin C metabolism. These share a common final pathway of a prothrombotic and proinflammatory state on the endothelial cell surface, with fibrin and platelet deposition. Much work has been done to distinguish between the different mechanisms of disease, thereby informing the optimal therapeutic interventions for each entity.

Eculizumab; Ravulizumab; Thrombotic microangiopathy Eculizumab; Ravulizumab; Microangiopatía trombótica Eculizumab; Ravulizumab; Microangiopatia trombòtica Ravulizumab, a long-acting complement C5 inhibitor engineered from eculizumab, allows extending maintenance dosing from every 2-3 weeks to every 4-8 weeks depending on bodyweight. Here, we evaluated the efficacy and safety of ravulizumab in complement inhibitor-naïve children (under 18 years) with atypical hemolytic uremic syndrome. In this phase III, single-arm trial, ravulizumab was administered every eight weeks in patients 20 kg and over, and four weeks in patients under 20 kg. The primary endpoint was a complete thrombotic microangiopathy response (normalization of platelet count and lactate dehydrogenase, and a 25% or more improvement in serum creatinine) through 26 weeks. Secondary endpoints included change in hematologic parameters and kidney function. 18 patients with a median age of 5.2 years were evaluated. At baseline, symptoms of atypical hemolytic uremic syndrome outside the kidney were present in 72.2% of patients and 38.9% had been in intensive care. Baseline estimated glomerular filtration rate was 22 mL/min/1.73 m2. By week 26, 77.8% of patients achieved a complete thrombotic microangiopathy response; 94.4%, 88.9% and 83.3% of patients achieved platelet normalization, lactate dehydrogenase normalization and a 25% or more improvement in serum creatinine, respectively. By week 50, 94.4% patients had achieved a complete thrombotic microangiopathy response. Median improvement in platelet count was 246 and 213 x109/L through week 26 and week 50, respectively. The median increase above baseline in estimated glomerular filtration rate was 80 and 94 mL/min/1.73m2 through week 26 and week 50, respectively. No unexpected adverse events, deaths, or meningococcal infections occurred. Thus, ravulizumab rapidly improved hematologic and kidney parameters with no unexpected safety concerns in complement inhibitor-naïve children with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome is a rare life-threatening disease of unregulated complement activation. Untreated, the prognosis is generally poor; more than one-half of patients die or develop end-stage renal disease within 1 year. Atypical hemolytic uremic syndrome is characterized by thrombotic microangiopathy with evidence of hemolysis, thrombocytopenia, and renal impairment. This systemic disease affects the kidneys, brain, heart, lungs, gastrointestinal tract, pancreas, and skin. Acquired and genetic abnormalities of complement regulation may be identified in approximately 70% of patients. Plasma therapy is generally ineffective. Eculizumab blocks terminal complement activation, prevents complement-mediated organ damage, and is currently recommended as front-line therapy.

Background Ravulizumab, a humanized anti-complement C5 monoclonal antibody designed by targeted modification of eculizumab to achieve an extended half-life, is approved to treat aHUS in the USA (2019), EU and Japan (2020). Data at 26 weeks (wk) and 1 year (yr) from the phase 3 studies of ravulizumab in adults and children with aHUS have been published. Here we report 2-yr data from these trials. Methods Efficacy and safety data from ravulizumab clinical trials in adults naïve to complement inhibitor treatment (NCT02949128), and in children either naïve to (naïve) or switched from (switch) eculizumab (NCT03131219), were assessed at 2 yr and presented alongside data from the initial 26-wk evaluation periods; patients were dosed every 8 wk (adult), or every 4 or 8 wk (children), according to body weight. Descriptive statistical analyses were conducted on these data. No statistical comparisons between data at 26 wk and 2 yr, or between trials, were conducted. Results Efficacy data in adults and treatment-naïve children are presented in the Table. Complete thrombotic microangiopathy (TMA) response (platelet count normalization, lactate dehydrogenase normalization, and ≥25% improvement in serum creatinine from baseline, met concurrently at 2 separate assessments, at least 4 wk apart) was achieved in more patients at 2 yr vs 26 wk in both studies (adult: 34 [61%) vs 30 [54%]; naïve: 18 [90%] vs 15 [75%]). All complete TMA response components were either numerically improved or maintained at 2 yr vs 26 wk. Kidney function continued to improve, with the median change in estimated glomerular filtration rate from baseline numerically increasing at 2 yr vs 26 wk in both adults (35 vs 29 mL/min/1.73m 2) and naïve children (82.5 vs 80 mL/min/1.73m 2). Most patients receiving dialysis at baseline were able to discontinue dialysis at 26 wk; this was sustained in adults (67% vs 67%) while all naïve children receiving dialysis at baseline had discontinued by 2 yr (83% vs 100%). No patients who discontinued dialysis by 26 wk subsequently restarted. Chronic kidney disease (CKD) stage improved in most patients through 26 wk in both studies (adult, 68%; naïve, 88%); improvements were sustained at 2 yr (adult, 71%; naïve, 94%). No naïve children experienced a worsening of CKD stage at 2 yr. Improvements from baseline in quality of life were seen at both 26 wk and 2 yr, as measured by Functional Assessment of Chronic Illness Therapy-Fatigue (adults: 20 vs 12; naïve: 10 vs 8), EQ-5D-3L visual analog scale (adults: 32 vs 33) and EQ-5D-3L time trade-off (adults: 0.32 vs 0.31). Most adverse events (AEs) and serious AEs (SAEs) occurring in these studies were reported during the initial 26-wk evaluation period, with a general reduction in the number of patients with any new S/AE events being reported at 2 yr. The most common AEs reported through 2 yr, which had not met the 15% reporting threshold through 26 wk, were (n, %): adults - constipation (9, 16%), fatigue (9, 16%) and nasopharyngitis (9, 16%); naïve children - abdominal pain (6, 25%), contusion (5, 21%), cough (5, 21%), nausea (4, 17%), myalgia (4, 17%), rash (4, 17%) and rhinorrhea (4, 17%); switch children - upper respiratory tract infections (URTI; 4, 40%), oropharyngeal pain (3, 30%), pharyngitis (3, 30%), cough (2, 20%), gastroenteritis (2, 20%), nasopharyngitis (2, 20%), otitis media (2, 20%), viral URTI (2, 20%) and dehydration (2, 20%). No patients discontinued either study due to treatment-emergent AEs after 26 wk. No meningococcal infections were recorded in either study at any timepoints. One adult patient, who had previously met complete TMA response criteria while receiving therapy, discontinued treatment by choice and subsequently experienced recurrent disease, as evidenced by an increase in serum creatinine (SCr). This patient then restarted therapy, leading to improvements in SCr levels. Conclusions In both treatment-naïve adults and children, ravulizumab was associated with numerically sustained or increased improvements in hematologic outcomes and kidney function at 2 yr vs 26 wk. Fewer S/AEs were reported during the extension period of these studies vs the initial 26-wk evaluation periods. Importantly, no meningococcal infections were reported in either study at any timepoint. The data suggest that long-term treatment with ravulizumab is well tolerated and may be associated with continuing improvements in TMA parameters and renal function in adults and children with aHUS. Figure 1 Figure 1. Disclosures Dixon: Apellis Pharmaceuticals: Consultancy; Horizon Pharmaceuticals: Consultancy; Alexion Pharmaceuticals: Consultancy. Kavanagh: Gyroscope Therapeutics: Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Apellis: Honoraria, Speakers Bureau; Idorsia: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Alexion Pharmaceuticals: Honoraria, Speakers Bureau. Kang: Alexion Pharmaceuticals: Honoraria, Research Funding; Handok: Honoraria; Kyowa Kirin: Honoraria, Research Funding; Amgen: Research Funding; Bayer: Research Funding. Wang: Alexion, AstraZeneca Rare Disease Inc.: Current Employment. Garlo: Alexion: Current Employment; AstraZeneca: Current Employment. Greenbaum: Alexion Pharmaceuticals: Honoraria, Research Funding. Ogawa: Alexion Pharmaceuticals: Current Employment. Cataland: Ablynx/Sanofi: Consultancy, Research Funding; Sanofi Genzyme: Consultancy; Alexion: Consultancy, Research Funding; Takeda: Consultancy. Miyakawa: Sanofi: Consultancy; Zenyaku Kogyo: Consultancy; Sanofi: Research Funding; argenx: Consultancy, Research Funding.

Primary cilia sense environmental conditions, including osmolality, but whether cilia participate in the osmotic response in renal epithelial cells is not known. The transient receptor potential (TRP) channels TRPV4 and TRPM3 are osmoresponsive. TRPV4 localizes to cilia in certain cell types, while renal subcellular localization of TRPM3 is not known. We hypothesized that primary cilia are required for maximal activation of the osmotic response of renal epithelial cells and that ciliary TRPM3 and TRPV4 mediate that response. Ciliated [murine epithelial cells from the renal inner medullary collecting duct (mIMCD-3) and 176-5] and nonciliated (176-5Δ) renal cells expressed Trpv4 and Trpm3. Ciliary expression of TRPM3 was observed in mIMCD-3 and 176-5 cells and in wild-type mouse kidney tissue. TRPV4 was identified in cilia and apical membrane of mIMCD-3 cells by electrophysiology and in the cell body by immunofluorescence. Hyperosmolal stress at 500 mOsm/kg (via NaCl addition) induced the osmotic response genes betaine/GABA transporter ( Bgt1) and aldose reductase ( Akr1b3) in all ciliated cell lines. This induction was attenuated in nonciliated cells. A TRPV4 agonist abrogated Bgt1 and Akr1b3 induction in ciliated and nonciliated cells. A TRPM3 agonist attenuated Bgt1 and Akr1b3 induction in ciliated cells only. TRPM3 knockout attenuated Akr1b3 induction. Viability under osmotic stress was greater in ciliated than nonciliated cells. Akr1b3 induction was also less in nonciliated than ciliated cells when mannitol was used to induce hyperosmolal stress. These findings suggest that primary cilia are required for the maximal osmotic response in renal epithelial cells and that TRPM3 is involved in this mechanism. TRPV4 appears to modulate the osmotic response independent of cilia.

Thrombotic microangiopathy (TMA) after hematopoietic stem cell transplantation (HSCT) associated with terminal complement activation, as measured by elevated plasma terminal complement (sC5b-9) concentrations, has a very high mortality. The complement inhibitor eculizumab may be a therapeutic option for HSCT-associated TMA. We examined the pharmacokinetics and pharmacodynamics (PK/PD) of eculizumab in children and young adult HSCT recipients with TMA and activated complement to determine drug dosing requirements for future efficacy trials. We analyzed prospectively collected laboratory samples and clinical data from 18 HSCT recipients with high-risk TMA presenting with complement activation who were treated with eculizumab. We measured eculizumab serum concentrations, total hemolytic complement activity, and plasma sC5b-9 concentrations. Population PK/PD analyses correlated eculizumab concentrations with complement blockade and clinical response and determined interindividual differences in PK parameters. We also compared transplant survival in patients treated with eculizumab (n = 18) with patients with the same high-risk TMA features who did not receive any targeted therapy during a separate prospective observational study (n = 11). In the PK analysis, we found significant interpatient variability in eculizumab clearance, ranging from 16 to 237 mL/hr/70 kg in the induction phase. The degree of complement activation measured by sC5b-9 concentrations at the start of therapy, in addition to actual body weight, was a significant determinant of eculizumab clearance and disease response. Sixty-one percent of treated patients had complete resolution of TMA and were able to safely discontinue eculizumab without disease recurrence. Overall survival was significantly higher in treated subjects compared with untreated patients (56% versus 9%, P = .003). Complement blocking therapy is associated with improved survival in HSCT patients with high-risk TMA who historically have dismal outcomes, but eculizumab pharmacokinetics in HSCT recipients differ significantly from reports in other diseases like atypical hemolytic uremic syndrome and paroxysmal nocturnal hemoglobinuria. Our eculizumab dosing algorithm, including pr-treatment plasma sC5b-9 concentrations, patient's actual body weight, and the first eculizumab dose (mg), accurately determined eculizumab concentration-time profiles for HSCT recipients with high-risk TMA. This algorithm may guide eculizumab treatment and ensure that future efficacy studies use the most clinically appropriate and cost-efficient dosing schedules.

Key Points Transplantation-associated thrombotic microangiopathy is associated with complement activation in vitro. This data further supports the use of eculizumab for the treatment of patients with TA-TMA.

PURPOSE OF REVIEW: This paper provides a review of the diagnostic evaluation of both microscopic and gross hematuria, as well as an update on the pathogenesis, clinical features, and treatment strategies for several diseases of the kidneys and urinary tract in which hematuria is a prominent finding. The goal is to provide pediatric providers with a framework through which appropriate and expeditious referral to subspecialty care may be made for definitive treatment. RECENT FINDINGS: Although there has been great heterogeneity in published treatment strategies for many causes of hematuria, the Kidney Diseases Improving Global Outcomes (KDIGO) initiative has recently set forth guidelines for glomerular diseases in particular to provide evidence-based strategies for treatment. In addition, recent advances in the understanding of molecular pathogenesis and long-term clinical outcomes for other non-glomerular diseases has led to updates in treatment strategies summarized in this review. SUMMARY: As the pediatric primary care provider is often the first point of contact for children with microscopic or gross hematuria, updated knowledge as to the epidemiology and management of several of the various causes of hematuria will improve the care of children by both avoiding extraneous testing and interventions and implementing definitive care (either by expectant management and reassurance or by subspecialty referral) in a timely manner.

Background: The 50% hemolytic complement (CH50) assay is a non-specific qualitative assay of complement function. CH50 is sometimes used in patients with complement-mediated thrombotic microangiopathy such as atypical hemolytic uremic syndrome (aHUS) to monitor response to complement inhibition. There are multiple commercial assays as well as research-based CH50 assays that are not directly comparable in outcomes or methods. Ravulizumab is a long-acting anti-C5 monoclonal antibody engineered from eculizumab, currently being investigated for the treatment of aHUS. A fully validated free C5 assay, supporting the primary pharmacodynamic endpoint, was utilized in clinical trials of ravulizumab. We have compared local CH50 results from participating sites with the free C5 assay, performed centrally, in patients with aHUS participating in the clinical trial. Methods: Adults and children with aHUS enrolled in phase 3 trials of ravulizumab (NCT02949128 and NCT03131219) were included in this analysis. A validated Gyros-based immunoassay with a fluorescence readout was used to quantify free C5 during the trial. The regulatory-accepted threshold for complete terminal complement inhibition is a free C5 value Results: CH50 data from 10 patients with aHUS (5 adults and 5 children) from four countries (US, Spain, France and UK) were available. A scatter plot of serum CH50 and free C5 versus time is shown in the figure. Complete terminal complement inhibition throughout the evaluation period was demonstrated by the free C5 assay. Results of CH50 did not consistently confirm full complement inhibition, demonstrating discordance with the free C5 assay. Relative to the adults, there was qualitatively more variability in the CH50 results in the pediatric patients. Conclusions: Results from the CH50 assays inconsistently demonstrated full complement inhibition, with discordance with free C5 levels. This discordance requires further investigation. In clinical practice, this has potential to cause different interpretations of complement blockade and highlights the important limitations of CH50 as a technique for assessing complete terminal complement blockade in patients receiving ravulizumab. This study also underscores the need for a commercially available validated measure for determining complement inhibition. Disclosures Cataland: Alexion: Consultancy, Research Funding; Ablynx/Sanofi: Consultancy, Research Funding. Ariceta:Alexion: Consultancy, Honoraria. Chen:Alexion: Employment. Dixon:Alexion: Consultancy; Apellis Pharmaceuticals: Consultancy; Horizon Pharmaceuticals: Consultancy. Garlo:Alexion: Employment. Greenbaum:Alexion: Consultancy, Honoraria, Research Funding. Rondeau:Alexion: Consultancy, Honoraria. Scully:Novartis: Consultancy; Shire: Research Funding; Shire/Takeda: Consultancy; Alexion: Consultancy; Ablynx/Sanofi: Consultancy. Ortiz:Alexion: Employment.

Hemolytic uremic syndrome (HUS) is a triad of thrombocytopenia, microangiopathic hemolysis, and acute kidney injury, within the broader category of thrombotic microangiopathy (TMA). The most common form of HUS in children is due to Shigatoxin-producing E. coli infection, although other forms due to invasive pneumococcal disease, genetic defects in complement regulation, and cobalamin C metabolism also occur. As the many forms of TMA share overlapping clinical features through the common pathomechanism of endothelial cell injury, laboratory investigation is warranted to provide additional diagnostic insight. Secondary forms of TMA also share clinical features with HUS, and although uncommon in children, should be excluded by careful assessment of the patient’s history and laboratory evaluation.

Renal cysts occur in approximately 50% of patients with tuberous sclerosis complex, but their clinical significance and response to treatment are unknown. Abdominal imaging of 15 patients with tuberous sclerosis complex-associated renal cystic disease who had received mammalian target of rapamycin inhibitor therapy for other tuberous sclerosis complex-related indications was evaluated. Reductions in cyst number, sum diameter, and volume were observed.

Nearly all patients with tuberous sclerosis complex (TSC) develop renal angiomyolipomas, although the tumor cell of origin is unknown. We observed decreased renal angiomyolipoma development in patients with TSC2- polycystic kidney disease 1 deletion syndrome and hypertension that were treated from an early age with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers compared with patients who did not receive this therapy. TSC-associated renal angiomyolipomas expressed ANG II type 1 receptors, platelet-derived growth factor receptor-β, desmin, α-smooth muscle actin, and VEGF receptor 2 but did not express the adipocyte marker S100 or the endothelial marker CD31. Sera of TSC patients exhibited increased vascular mural cell-secreted peptides, such as VEGF-A, VEGF-D, soluble VEGF receptor 2, and collagen type IV. These findings suggest that angiomyolipomas may arise from renal pericytes. ANG II treatment of angiomyolipoma cells in vitro resulted in an exaggerated intracellular Ca2+response and increased proliferation, which were blocked by the ANG II type 2 receptor antagonist valsartan. Blockade of ANG II signaling may have preventative therapeutic potential for angiomyolipomas.

We recently observed that dysregulation of the complement system may be involved in the pathogenesis of hematopoietic stem cell transplantation–associated thrombotic microangiopathy (HSCT-TMA). These findings suggest that the complement inhibitor eculizumab could be a therapeutic option for this severe HSCT complication with high mortality. However, the efficacy of eculizumab in children with HSCT-TMA and its dosing requirements are not known. We treated 6 children with severe HSCT-TMA using eculizumab and adjusted the dose to achieve a therapeutic level >99 μg/mL. HSCT-TMA resolved over time in 4 of 6 children after achieving therapeutic eculizumab levels and complete complement blockade, as measured by low total hemolytic complement activity (CH50). To achieve therapeutic drug levels and a clinical response, children with HSCT-TMA required higher doses or more frequent eculizumab infusions than currently recommended for children with atypical hemolytic uremic syndrome. Two critically ill patients failed to reach therapeutic eculizumab levels, even after dose escalation, and subsequently died. Our data indicate that eculizumab may be a therapeutic option for HSCT-TMA, but HSCT patients appear to require higher medication dosing than recommended for other conditions. We also observed that a CH50 level ≤ 4 complement activity enzyme units correlated with therapeutic eculizumab levels and clinical response, and therefore CH50 may be useful to guide eculizumab dosing in HSCT patients as drug level monitoring is not readily available.

Primary cilia of renal epithelial cells express several members of the transient receptor potential (TRP) class of cation-conducting channel, including TRPC1, TRPM3, TRPM4, TRPP2, and TRPV4. Some cases of autosomal dominant polycystic kidney disease (ADPKD) are caused by defects in TRPP2 (also called polycystin-2, PC2, or PKD2). A large-conductance, TRPP2-dependent channel in renal cilia has been well described, but it is not known whether this channel includes any other protein subunits. To study this question, we investigated the pharmacology of the TRPP2-dependent channel through electrical recordings from the cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin. The pharmacology was found to match that of TRPM3 channels. The ciliary TRPP2-dependent channel is known to be activated by depolarization and by increasing cytoplasmic Ca2+. This activation was greatly enhanced by external pregnenolone sulfate, an agonist of TRPM3 channels. Pregnenolone sulfate did not change the single-channel current-voltage relation. The channels were effectively blocked by isosakuranetin, a specific inhibitor of TRPM3 channels. Both pregnenolone sulfate and isosakuranetin were effective at concentrations as low as 1 μM. Knocking out TRPM3 by CRISPR/Cas9 genome editing eliminated the ciliary channel. Thus the channel is both TRPM3-dependent and TRPP2-dependent, suggesting that it may include both types of subunit. Knocking out TRPM3 did not change the level of TRPP2 protein in the cilia, so it is unlikely that the absence of functional ciliary channels results from a failure of trafficking.

Novel Urinary Biomarkers of Early Acute Kidney Injury in Pediatric Stem Cell Transplantation Acute kidney injury (AKI) is a common complication in pediatric stem cell transplantation (SCT). Creatinine is a late biomarker of AKI. Several novel urinary biomarkers that predict AKI have been proposed. We evaluated the sequential patterns of biomarker elevation after SCT to determine their diagnostic accuracy. We measured urine neutrophil gelatinase associated lipocalin (NGAL), monocyte chemoattractant protein 1 (MCP1), kidney injury molecule 1 (KIM1), vitamin D binding protein (VDBP), and albumin using urine prospectively collected from consecutive pediatric allogeneic SCT patients at baseline and days 0, 14, and 28 using commercial ELISA assays validated for use with urine. Association of AKI (≥50% increase in serum creatinine from baseline) in the first 28 days of HSCT with patient, primary disease, and SCT characteristics was assessed (Table 1), for which only exposure to chemotherapy prior to SCT was significant. We then analyzed the association between each biomarker with the clinical outcome of AKI in the first 28 days of SCT. Of the 80 patients examined, AKI developed in 18 patients. Elevations of MCP1 and NGAL at day 14, and elevations in MCP1 and KIM1 at day 28 were significantly higher in patients who developed AKI (Figure 1). Albuminuria, the most traditional urinary biomarker, showed no discriminating ability. MCP1, KIM1, and NGAL are promising novel biomarkers of early AKI in SCT. Urinary biomarkers could improve renal outcomes in stem cell transplantation by enabling earlier identification of acute kidney injury.

Hematopoietic stem cell transplant (HSCT)-associated thrombotic microangiopathy (TMA) is a complication that occurs in 25% to 35% of HSCT recipients and shares histomorphologic similarities with hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). The hallmark of all thrombotic microangiopathies is vascular endothelial cell injury of various origins, resulting in microangiopathic hemolytic anemia, platelet consumption, fibrin deposition in the microcirculation, and tissue damage. Although significant advances have been made in understanding the pathogenesis of other thrombotic microangiopathies, post-HSCT TMA remains poorly understood. We report an analysis of the complement alternative pathway, which has recently been linked to the pathogenesis of both the Shiga toxin mediated and the atypical forms of HUS, with a focus on genetic variations in the complement Factor H (CFH) gene cluster and CFH autoantibodies in six children with post-HSCT TMA. We identified a high prevalence of deletions in CFH-related genes 3 and 1 (delCFHR3-CFHR1) and CFH autoantibodies in these patients with HSCT-TMA. Conversely, CFH autoantibodies were not detected in 18 children undergoing HSCT who did not develop TMA. Our observations suggest that complement alternative pathway dysregulation may be involved in the pathogenesis of post-HSCT TMA. These findings shed light on a novel mechanism of endothelial injury in transplant-TMA and may therefore guide the development of targeted treatment interventions.

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder affecting almost all organs. It has wider phenotypic variation than often appreciated, with less than half showing the combination of characteristic facial angiofibromas, epilepsy, and mental retardation. Renal angiomyolipomata or cysts are found in 90% and renal failure was historically a common mode of adult death from the disease. Pulmonary lymphangioleiomyomatosis is restricted to females. Angiomyolipomata or cystic disease, or both, may cause renal failure. Angiomyolipomata may also haemorrhage, especially from larger lesions. Manifestations of brain involvement substantially complicate management of many patients with TSC. The causative genes TSC1 and TSC2 encode tuberin and hamartin which are involved in control of the mammalian target of rapamycin pathway. Inhibitors of that pathway, such as sirolimus and everolimus, are therefore logical approaches to therapy and have been shown to be effective in reducing angiomyolipomata volume. It remains to be seen whether they can protect renal function.

Patients who have had surgical bladder augmentation have an increased risk of bladder malignancy, though the mechanism for this increased risk is unknown. Hyperosmolal microenvironments such as the bladder may impair DNA damage signaling and repair; this effect may be more pronounced in tissues not normally exposed to such conditions. Comparing gastric and colon epithelial cell lines to transitional epithelial cell lines gradually adapted to an osmolality of 600 mOsm/kg with either sodium chloride or urea, cell lines of gastrointestinal origin were inhibited in their ability to activate ATM and downstream effectors of DNA damage signaling and repair such as p53, Nbs1, replication protein A (RPA), and gammaH2AX following the induction of DNA damage with etoposide. In contrast, bladder cell lines demonstrated a preserved ability to phosphorylate ATM and its effectors under conditions of hyperosmolal urea, and to a lesser extent with sodium chloride. The bladder cell lines' ability to respond to DNA damage under hyperosmolal conditions may be due in part to protective mechanisms such as the accumulation of intracellular organic osmolytes and the uroplakin-containing asymmetric unit membrane as found in transitional epithelial cells, but not in gastrointestinal cells. Failure of such protective adaptations in the tissues used for augmentation cystoplasties may place these tissues at increased risk for malignancy.

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is now a well-recognized and potentially severe complication of HSCT that carries a high risk of death. In those who survive, TA-TMA may be associated with long-term morbidity and chronic organ injury. Recently, there have been new insights into the incidence, pathophysiology, and management of TA-TMA. Specifically, TA-TMA can manifest as a multi-system disease occurring after various triggers of small vessel endothelial injury, leading to subsequent tissue damage in different organs. While the kidney is most commonly affected, TA-TMA involving organs such as the lung, bowel, heart, and brain is now known to have specific clinical presentations. We now review the most up-to-date research on TA-TMA, focusing on the pathogenesis of endothelial injury, the diagnosis of TA-TMA affecting the kidney and other organs, and new clinical approaches to the management of this complication after HSCT.

This report describes severe hypertension in a 7-week-old male infant found to have renovascular disease from an organized hematoma due to prenatal trauma. As such, this case illustrates a novel acquired, congenital mechanism of renovascular hypertension. The importance of considering prenatal as well as postnatal etiologies of acquired renovascular hypertension in neonates is emphasized. Likewise, attention must be drawn to the classic presentation of congestive heart failure in a child with severe hypertension.

Tuberous sclerosis complex (TSC), an inherited tumor predisposition syndrome associated with mutations in TSC1 or TSC2, affects ∼1 in 6,000 individuals. Eighty percent of TSC patients develop renal angiomyolipomas, and renal involvement is a major contributor to patient morbidity and mortality. Recent work has shown that mammalian target of rapamycin complex 1 (mTORC1) inhibition caused angiomyolipoma shrinkage but that this treatment may cause cytostatic not a cytotoxic effect. Endoplasmic reticulum (ER) stress can develop in TSC-associated cells due to mTORC1-driven protein translation. We hypothesized that renal angiomyolipoma cells experience ER stress that can be leveraged to result in targeted cytotoxicity. We used immortalized human angiomyolipoma cells stably transfected with empty vector or TSC2 (encoding tuberin). Using cell number quantification and cell death assays, we found that mTORC1 inhibition with RAD001 suppressed angiomyolipoma cell proliferation in a cytostatic manner. Angiomyolipoma cells exhibited enhanced sensitivity to proteasome inhibitor-induced ER stress compared with TSC2-rescued cells. After proteasome inhibition with MG-132, Western blot analyses showed greater induction of C/EBP-homologous protein (CHOP) and more poly (ADP-ribose) polymerase (PARP) and caspase-3 cleavage, supporting ER stress-induced apoptosis. Live cell numbers also were decreased and cell death increased by MG-132 in angiomyolipoma cells compared with TSC2 rescued. Intriguingly, while pretreatment of angiomyolipoma cells with RAD001 attenuated CHOP and BiP induction, apoptotic markers cleaved PARP and caspase-3 and eukaryotic translation initiation factor 2α phosphorylation were increased, along with evidence of increased autophagy. These results suggest that human angiomyolipoma cells are uniquely susceptible to agents that exacerbate ER stress and that additional synergy may be achievable with targeted combination therapy.