Sodium-glucose cotransporter 2 inhibition in primary and secondary glomerulonephritis

BACKGROUND

The role of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in the management glomerular/systemic autoimmune diseases with proteinuria in real-world clinical settings is unclear.

METHODS

This is a retrospective, observational, international cohort study. Adult patients with biopsy-proven glomerular diseases were included. The main outcome was the percentage reduction in 24-h proteinuria from SGLT2i initiation to 3, 6, 9 and 12 months. Secondary outcomes included percentage change in estimated glomerular filtration rate (eGFR), proteinuria reduction by type of disease and reduction of proteinuria ≥30% from SGLT2i initiation.

RESULTS

Four-hundred and ninety-three patients with a median age of 55 years and background therapy with renin-angiotensin system blockers were included. Proteinuria from baseline changed by -35%, -41%, -45% and -48% at 3, 6, 9 and 12 months after SGLT2i initiation, while eGFR changed by -6%, -3%, -8% and -10.5% at 3, 6, 9 and 12 months, respectively. Results were similar irrespective of the underlying disease. A correlation was found between body mass index (BMI) and percentage proteinuria reduction at last follow-up. By mixed-effects logistic regression model, serum albumin at SGLT2i initiation emerged as a predictor of ≥30% proteinuria reduction (odds ratio for albumin <3.5 g/dL, 0.53; 95% CI 0.30-0.91; P = .02). A slower eGFR decline was observed in patients achieving a ≥30% proteinuria reduction: -3.7 versus -5.3 mL/min/1.73 m2/year (P = .001). The overall tolerance to SGLT2i was good.

CONCLUSIONS

The use of SGLT2i was associated with a significant reduction of proteinuria. This percentage change is greater in patients with higher BMI. Higher serum albumin at SGLT2i onset is associated with higher probability of achieving a ≥30% proteinuria reduction.

Cystic phenotype and chronic kidney disease in autosomal dominant Alport syndrome

BACKGROUND AND HYPOTHESIS

Autosomal Dominant Alport Syndrome (ADAS), also known as Thin Basement Membrane Disease (TBMD), is caused by pathogenic variants in COL4A3 and COL4A4 genes. A cystic phenotype has been described in some patients with TBMD, but no genetic studies were performed. We conducted a genetic and radiologic investigation in a cohort of ADAS patients to analyze the prevalence of multicystic kidney disease (MKD) and its association with Chronic Kidney Disease (CKD).

METHODS

Retrospective single-center cohort study. Thirty-one patients showing pathogenic or likely pathogenic variants in COL4A3 or COL4A4 from a cohort of 79 patients with persistent microscopic hematuria were included. Mean follow-up was 9.4±9.6 years. The primary objective of the study was to determine the prevalence of MKD in the cohort of ADAS patients. Secondary objectives were to determine risk factors associated with an eGFR<45 ml/min/1.73m2 at the time of genetic and radiologic evaluation and to investigate the coexistence of other genetic abnormalities associated with familial hematuria and cystic kidney disease.

RESULTS

MKD was found in 16 patients (52%). Mean number of cysts per kidney was 12.7±5.5. No genetic abnormalities were found in a panel of 101 other genes related to familial hematuria, focal segmental glomerulosclerosis and cystic kidney disease. A greater number of patients with MKD had an eGFR<45 ml/min/1.73m2 (63% vs 7%, p=0.006) and more advanced CKD than patients without MKD. The annual rate of eGFR decline was greater in patients with MKD: -1.8 vs 0.06 ml/min/1.73m2/year (p=0.009). By multivariable linear regression analysis, the main determinants of eGFR change per year were time-averaged proteinuria (p=0.002) and MKD (p=0.02).

CONCLUSION

MKD is commonly found in ADAS and is associated with a worse kidney outcome. No pathogenic variants were found in genes other than COL4A3/COL4A4.

Complement alternative pathway determines disease susceptibility and severity in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis

Activation of the alternative pathway (AP) of complement is involved in the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), although the underlying molecular mechanisms are unclear. To gain insight into the role of the AP, common gene variants in CFH/CFHR1-5, CFB, C3 and MCP, and longitudinal determinations of plasma C3, C4, FH, FHR-1, FHR-2, FHR-5, FB, properdin and sC5b-9 levels were analyzed in a Spanish AAV cohort consisting of 102 patients; 54 with active AAV (active cohort) and 48 in remission not receiving immunosuppressants or dialysis therapy (remission cohort). The validation cohort consisted of 100 patients with ANCA-associated glomerulonephritis. Here, we demonstrated that common genetic variants in complement components of the AP are associated with disease susceptibility (CFB32Q/W) or severity of kidney damage in AAV (CFH-H1, CFH1H2 and ΔCFHR3/1). Plasma levels of complement components were significantly different between active and remission cohorts. In longitudinal observations, a high degree of AP activation at diagnosis was associated with worse disease outcome, while high basal FHR-1 levels and lower FH/FHR-1 ratios determined severe forms of kidney associated AAV. These genetic and plasmatic findings were confirmed in the validation cohort. Additionally, autoantibodies against FH and C3 convertase were identified in one and five active patients, respectively. Thus, our study identified key genetic and plasma components of the AP that determine disease susceptibility, prognosis, and severity in AAV. Our data also suggests that balance between FH and FHR-1 is critical and supports FHR-1 as a novel AP-specific therapeutic target in AAV.

Targeting complement in IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Recent years have witnessed significant improvements in the understanding of the pathogenesis of IgAN and particularly, the pathogenic role of complement activation. The alternative complement pathway is the major complement cascade activator in IgAN, and glomerular C3 deposition has been shown to correlate with disease progression. In addition, several studies have provided insight into the pathogenic role of factor H-related proteins -1 and -5 in IgAN, as independent players in complement dysregulation. The lectin pathway has also been shown to be associated with the severity of IgAN. Glomerular deposition of C4d has been associated with increased histologic disease activity, faster decline in estimated glomerular filtration rate and higher risk of kidney failure. On the other hand, although overlooked in the Oxford classification, numerous studies have shown that the coexistence of thrombotic microangiopathy in IgAN is a significant indicator of a poorer prognosis. All the breakthroughs in the understanding of the contributing role of complement in IgAN have paved the way for the development of new complement-targeted therapies in this disease. Several ongoing trials are evaluating the efficacy of new agents against factor B (iptacopan, Ionis-FB-LRX), C3 (pegcetacoplan), factor D (vemircopan, pelecopan), C5 (ravulizumab, cemdisiran) and C5a receptor 1 (avacopan). In this study, we provide a comprehensive review of the role of complement in IgAN, including the emerging mechanisms of complement activation and the promising potential of complement inhibitors as a viable treatment option for IgAN.

High exposure to tacrolimus is associated with spontaneous remission of recurrent membranous nephropathy after kidney transplantation

Introduction

We aimed to characterize the incidence and clinical presentation of membranous nephropathy (MN) after kidney transplantation (KT), and to assess allograft outcomes according to proteinuria rates and immunosuppression management.

Methods

Multicenter retrospective cohort study including patients from six Spanish centers who received a KT between 1991-2019. Demographic, clinical, and histological data were collected from recipients with biopsy-proven MN as primary kidney disease (n = 71) or MN diagnosed de novo after KT (n = 4).

Results

Up to 25.4% of patients with biopsy-proven MN as primary kidney disease recurred after a median time of 18.1 months posttransplant, without a clear impact on graft survival. Proteinuria at 3-months post-KT was a predictor for MN recurrence (rMN, HR 4.28; P = 0.008). Patients who lost their grafts had higher proteinuria during follow-up [1.0 (0.5-2.5) vs 0.3 (0.1-0.5) g/24 h], but only eGFR after recurrence treatment predicted poorer graft survival (eGFR < 30 ml/min: RR = 6.8). We did not observe an association between maintenance immunosuppression and recurrence diagnosis. Spontaneous remission after rMN was associated with a higher exposure to tacrolimus before recurrence (trough concentration/dose ratio: 2.86 vs 1.18; P = 0.028). Up to 94.4% of KT recipients received one or several treatments after recurrence onset: 22.2% rituximab, 38.9% increased corticosteroid dose, and 66.7% ACEi/ARBs. Only 21 patients had proper antiPLA2R immunological monitoring.

Conclusions

One-fourth of patients with biopsy-proven MN as primary kidney disease recurred after KT, without a clear impact on graft survival. Spontaneous remission after rMN was associated with a higher exposure to tacrolimus before recurrence.

Future landscape for the management of membranous nephropathy

Among all glomerular diseases, membranous nephropathy (MN) is perhaps the one in which major progress has been made in recent decades, in both the understanding of the pathogenesis and treatment. Despite the overall significant response rates to these therapies-particularly rituximab and cyclical regimen based on corticosteroids and cyclophosphamide-cumulative experience over the years has shown, however, that 20%-30% of cases may confront resistant disease. Thus, these unmet challenges in the treatment of resistant forms of MN require newer approaches. Several emerging new agents-developed primarily for the treatment of hematological malignancies or rheumatoid diseases-are currently being evaluated in MN. Herein we conducted a narrative review on future therapeutic strategies in the disease. Among the different novel therapies, newer anti-CD20 agents (e.g. obinutuzumab), anti-CD38 (e.g. daratumumab, felzartamab), immunoadsorption or anti-complement therapies (e.g. iptacopan) have gained special attention. In addition, several technologies and innovations developed primarily for cancer (e.g. chimeric antigen receptor T-cell therapy, sweeping antibodies) seem particularly promising. In summary, the future therapeutic landscape in MN seems encouraging and will definitely move the management of this disease towards a more precision-based approach.

Effect of Immunosuppressive Treatments on Kidney Outcomes After Gross Hematuria-Related Acute Kidney Injury in Older Patients With IgA Nephropathy

Introduction

Macroscopic hematuria (MH) bouts, frequently accompanied by acute kidney injury (AKI-MH) are one of the most common presentations of IgA nephropathy (IgAN) in the elderly. Immunosuppressive therapies are used in clinical practice; however, no studies have analyzed their efficacy on kidney outcomes.

Methods

This is a retrospective, multicenter study of a cohort of patients aged ≥50 years with biopsy-proven IgAN presenting with AKI-MH. Outcomes were complete, partial, or no recovery of kidney function at 1 year after AKI-MH, and kidney survival at 1, 2, and 5 years. Propensity score matching (PSM) analysis was applied to balance baseline differences between patients treated with immunosuppression and those not treated with immunosuppression.

Results

The study group consisted of 91 patients with a mean age of 65 ± 15 years, with a mean follow-up of 59 ± 36 months. Intratubular red blood cell (RBC) casts and acute tubular necrosis were found in all kidney biopsies. The frequency of endocapillary hypercellularity and crescents were low. Immunosuppressive therapies (corticosteroids alone or combined with mycophenolate mofetil or cyclophosphamide) were prescribed in 52 (57%) patients, whereas 39 (43%) received conservative treatment. There were no significant differences in the proportion of patients with complete, partial, or no recovery of kidney function at 1 year between patients treated with immunosuppression and those not treated with immunosuppression (29% vs. 36%, 30.8% vs. 20.5% and 40.4 % vs. 43.6%, respectively). Kidney survival at 1, 3, and 5 years was similar among treated and untreated patients (85% vs. 81%, 77% vs. 76% and 72% vs. 66%, respectively). Despite the PSM analysis, no significant differences were observed in kidney survival between the two groups. Fourteen patients (27%) treated with immunosuppression had serious adverse events.

Conclusions

Immunosuppressive treatments do not modify the unfavorable prognosis of patients with IgAN who are aged ≥50 years presenting with AKI-MH, and are frequently associated with severe complications.

A meta-analysis of GFR slope as a surrogate endpoint for kidney failure

Glomerular filtration rate (GFR) decline is causally associated with kidney failure and is a candidate surrogate endpoint for clinical trials of chronic kidney disease (CKD) progression. Analyses across a diverse spectrum of interventions and populations is required for acceptance of GFR decline as an endpoint. In an analysis of individual participant data, for each of 66 studies (total of 186,312 participants), we estimated treatment effects on the total GFR slope, computed from baseline to 3 years, and chronic slope, starting at 3 months after randomization, and on the clinical endpoint (doubling of serum creatinine, GFR < 15 ml min-1 per 1.73 m2 or kidney failure with replacement therapy). We used a Bayesian mixed-effects meta-regression model to relate treatment effects on GFR slope with those on the clinical endpoint across all studies and by disease groups (diabetes, glomerular diseases, CKD or cardiovascular diseases). Treatment effects on the clinical endpoint were strongly associated with treatment effects on total slope (median coefficient of determination (R2) = 0.97 (95% Bayesian credible interval (BCI) 0.82-1.00)) and moderately associated with those on chronic slope (R2 = 0.55 (95% BCI 0.25-0.77)). There was no evidence of heterogeneity across disease. Our results support the use of total slope as a primary endpoint for clinical trials of CKD progression.

Epidemiology of Fabry disease in patients in hemodialysis in the Madrid community

This study screened for Fabry disease (FD) in patients in hemodialysis (HD) in the region of Madrid (CAM) with a cross-sectional design to evaluate HD-prevalent patients, followed by a three-year period prospective design to analyze HD-incident patients.

INCLUSION CRITERIA

patients older than 18 years on HD in the CAM, excluding patients diagnosed with any other hereditary disease with renal involvement different from FD, that sign the Informed Consent (IC).

EXCLUSION CRITERIA

underaged patients or not agreeing or not being capable of signing the IC.

RESULTS

3470 patients were included, 63% males and with an average age of 67.9±9.7 years. 2357 were HD-prevalent patients and 1113 HD-incident patients. For HD-prevalent patients, average time in HD was 45.2 months (SD 51.3), in HD-incident patients proteinuria was present in 28.4%. There were no statistical differences in plasmatic alpha-galactosidase A (α-GAL-A) activity or Lyso-GL-3 values when comparing HD-prevalent and HD-incident populations and neither between males and females. A genetic study was performed in 87 patients (2.5% of patients): 60 male patients with decreased enzymatic activity and 27 female patients either with a decreased GLA activity, increased Lyso-Gl3 levels or both. The genetic variants identified were: p.Asp313Tyr (4 patients), p.Arg220Gln (3 patients) and M290I (1 patient). None of the identified variants is pathogenic.

CONCLUSIONS

76% of HD Centers of the CAM participated in the study. This is the first publication to describe the prevalence of FD in the HD-population of a region of Spain as well as its average α-GAL-A-activity and plasmatic Lyso-Gl3 levels. It is also the first study that combines a cross-sectional design with a prospective follow-up design. This study has not identified any FD patient.

Role of light chain clearance in the recovery of renal function in multiple myeloma: another point of view

BACKGROUND

Acute kidney injury (AKI) in patients with multiple myeloma (MM) requiring renal replacement treatment (RRT) is associated with high morbidity and mortality. Early reduction of serum free light chains (FLC) using both targeted therapy against MM and intensive hemodialysis (IHD) may improve renal outcomes. We evaluated the effectiveness of two different RRT techniques on renal recovery in an MM patient population: standard dialysis procedure vs IHD with either polymethylmethacrylate (PMMA) or hemodiafiltration with endogenous reinfusion (HFR).

METHODS

This was a multicentric retrospective study with severe AKI related to MM, between 2011 and 2018. Twenty-five consecutive patients with AKI secondary to MM requiring RRT were included. Patients that underwent IHD received six dialysis sessions per week during the first 14 days (PMMA vs HFR). All patients were diagnosed with de novo MM or first relapsed MM. Primary outcome was renal recovery defined as dialysis-free at 6 months follow-up.

RESULTS

A total of 25 patients were included. Seventeen patients received IHD and eight standard dialysis. All patients were treated with targeted therapy, 84% bortezomib-based. Of the 25 patients included, 14 (56%) became dialysis independent. We observed a higher proportion of patients who received IHD in the group who recovered kidney function compared with those who remained in HD (92.9% vs 36.4%, P = .007). In our study, the use of IHD to remove FLC had a statistically significant association with renal recovery compared with the standard dialysis group (P = .024).

CONCLUSION

Early reduction of FLC with IHD as an adjuvant treatment along with MM-targeted therapy may exert a positive impact on renal recovery.

Clinical Profiles and Patterns of Kidney Disease Progression in C3 Glomerulopathy

Key Points

Kidney survival in C3 glomerulopathy is significantly higher in patients with a disease chronicity score <4 and proteinuria <3.5 g/d, regardless of baseline eGFR. A faster eGFR decline in C3 glomerulopathy is associated with higher probability of kidney failure. Patients with glomerulopathy with a progressive reduction in proteinuria over time did not reach kidney failure.

Background

C3 glomerulopathy is a rare kidney disease, which makes it difficult to collect large cohorts of patients to better understand its variability. The aims of this study were to describe the clinical profiles and patterns of progression of kidney disease.

Methods

This was a retrospective, observational cohort study. Patients diagnosed with C3 glomerulopathy between 1995 and 2020 were enrolled. Study population was divided into clinical profiles by combining the following predictors: eGFR under/above 30 ml/min per 1.73 m2, proteinuria under/above 3.5 g/d, and histologic chronicity score under/above 4. The change in eGFR and proteinuria over time was evaluated in a subgroup with consecutive measurements of eGFR and proteinuria.

Results

One hundred and fifteen patients with a median age of 30 years (interquartile range 19–50) were included. Patients were divided into eight clinical profiles. Kidney survival was significantly higher in patients with a chronicity score <4 and proteinuria <3.5 g/d, both in those presenting with an eGFR under/above 30 ml/min per 1.73 m2. The median eGFR slope of patients who reached kidney failure was −6.5 ml/min per 1.73 m2 per year (interquartile range −1.6 to −17). Patients who showed a reduction in proteinuria over time did not reach kidney failure. On the basis of the rate of eGFR decline, patients were classified as faster eGFR decline (≥5 ml/min per 1.73 m2 per year), slower (<5 ml/min per 1.73 m2 per year), and those without decline. A faster eGFR decline was associated with higher probability of kidney failure.

Conclusions

Kidney survival is significantly higher in patients with a chronicity score <4 and proteinuria <3.5 g/d regardless of baseline eGFR, and a faster rate of decline in eGFR is associated with higher probability of kidney failure.

Evaluation of Variation in the Performance of GFR Slope as a Surrogate End Point for Kidney Failure in Clinical Trials that Differ by Severity of CKD

BACKGROUND

The GFR slope has been evaluated as a surrogate end point for kidney failure in meta-analyses on a broad collection of randomized controlled trials (RCTs) in CKD. These analyses evaluate how accurately a treatment effect on GFR slope predicts a treatment effect on kidney failure. We sought to determine whether severity of CKD in the patient population modifies the performance of GFR slope.

METHODS

We performed Bayesian meta-regression analyses on 66 CKD RCTs to evaluate associations between effects on GFR slope (the chronic slope and the total slope over 3 years, expressed as mean differences in ml/min per 1.73 m2/yr) and those of the clinical end point (doubling of serum creatinine, GFR <15 ml/min per 1.73 m2, or kidney failure, expressed as a log-hazard ratio), where models allow interaction with variables defining disease severity. We evaluated three measures (baseline GFR in 10 ml/min per 1.73 m2, baseline urine albumin-to-creatinine ratio [UACR] per doubling in mg/g, and CKD progression rate defined as the control arm chronic slope, in ml/min per 1.73 m2/yr) and defined strong evidence for modification when 95% posterior credible intervals for interaction terms excluded zero.

RESULTS

There was no evidence for modification by disease severity when evaluating 3-year total slope (95% credible intervals for the interaction slope: baseline GFR [-0.05 to 0.03]; baseline UACR [-0.02 to 0.04]; CKD progression rate [-0.07 to 0.02]). There was strong evidence for modification in evaluations of chronic slope (95% credible intervals: baseline GFR [0.02 to 0.11]; baseline UACR [-0.11 to -0.02]; CKD progression rate [0.01 to 0.15]).

CONCLUSIONS

These analyses indicate consistency of the performance of total slope over 3 years, which provides further evidence for its validity as a surrogate end point in RCTs representing varied CKD populations.

Recurrence of immune complex and complement-mediated membranoproliferative glomerulonephritis in kidney transplantation

INTRODUCTION

Membranoproliferative glomerulonephritis (MPGN) represents a histologic pattern of glomerular injury that may be due to several aetiologies. Few studies have comprehensively analysed the recurrence of MPGN according to the current classification system.

METHODS

We collected a multicentre, retrospective cohort of 220 kidney graft recipients with biopsy-proven native kidney disease due to MPGN between 1981 and 2021 in 11 hospitals. Demographic, clinical and histologic parameters of prognostic interest were collected. The main outcomes were time to kidney failure, time to recurrence of MPGN and disease remission after recurrence.

RESULTS

The study group included 34 complement-mediated and 186 immune complex-mediated MPGN. A total of 81 patients (37%) reached kidney failure in a median follow-up of 79 months. The main predictors of this event were the development of rejection episodes and disease recurrence. In all, 54 patients (25%) had a disease recurrence in a median of 16 months after kidney transplantation. The incidence of recurrence was higher in patients with dysproteinaemia (67%) and complement-mediated MPGN (62%). In the multivariable model, complement-mediated MPGN emerged as a predictor of recurrence. A total of 33 patients reached kidney failure after recurrence. The main determinants of no remission were early time to recurrence (<15 months), estimated glomerular filtration rate <30 mL/min/1.73 m2 and serum albumin <3.5 g/dL at the time of recurrence.

CONCLUSIONS

One-fourth of the patients with native kidney disease due to MPGN developed clinical recurrence in the allograft, especially in cases with complement-mediated disease or in those associated with dysproteinaemia. The kidney outcomes of disease recurrence with currently available therapies are heterogeneous and thus more effective and individualized therapies are needed.

Thrombotic microangiopathy in patients with malignant hypertension

BACKGROUND

Thrombotic microangiopathy (TMA) is a complication of malignant hypertension (mHTN) attributed to the high levels of blood pressure (BP). However, no studies have investigated in patients with mHTN of different etiologies whether the presence of TMA is associated with specific causes of mHTN.

METHODS

We investigate the presence of TMA (microangiopathic hemolytic anemia and thrombocytopenia) in a large and well characterized cohort of 199 patients with mHTN of different etiologies (primary HTN 44%, glomerular diseases 16.6%, primary atypical hemolytic uremic syndrome (aHUS) 13.1%, renovascular HTN 9.5%, drug-related HTN 7%, systemic diseases 5.5%, endocrine diseases 4.5%). Outcomes of the study were kidney recovery and kidney failure.

RESULTS

Patients with TMA (40 cases, 20.1%) were younger, had a lower proportion of males, lower BP levels and worse kidney function at presentation. Their underlying diseases were primary aHUS (60%), drug-related mHTN (15%), glomerular diseases (all of them IgA nephropathy) (10%), systemic diseases (10%) and primary HTN (5%). The presence of TMA was 92.3% in primary aHUS, 42.9% in drug-related HTN, 36.4% in systemic diseases, 12.1% in glomerular diseases and 2.3% in primary HTN. No patient with renovascular HTN or mHTN caused by endocrine diseases developed TMA, despite BP levels as severe as patients with TMA. A higher proportion of TMA patients developed kidney failure as compared to patients without TMA (56.4% versus 38.9%, respectively).

CONCLUSIONS

The presence of TMA in patients with mHTN should guide the diagnosis towards primary aHUS, drug-related mHTN, some systemic diseases and IgA nephropathy, while it is exceptional in other causes of mHTN.

Factor H-Related Protein 1 Drives Disease Susceptibility and Prognosis in C3 Glomerulopathy

BACKGROUND

C3 glomerulopathy (C3G) is a heterogeneous group of chronic renal diseases characterized predominantly by glomerular C3 deposition and complement dysregulation. Mutations in factor H-related (FHR) proteins resulting in duplicated dimerization domains are prototypical of C3G, although the underlying pathogenic mechanism is unclear.

METHODS

Using in vitro and in vivo assays, we performed extensive characterization of an FHR-1 mutant with a duplicated dimerization domain. To assess the FHR-1 mutant's association with disease susceptibility and renal prognosis, we also analyzed CFHR1 copy number variations and FHR-1 plasma levels in two Spanish C3G cohorts and in a control population.

RESULTS

Duplication of the dimerization domain conferred FHR-1 with an increased capacity to interact with C3-opsonized surfaces, which resulted in an excessive activation of the alternative pathway. This activation does not involve C3b binding competition with factor H. These findings support a scenario in which mutant FHR-1 binds to C3-activated fragments and recruits native C3 and C3b; this leads to formation of alternative pathway C3 convertases, which increases deposition of C3b molecules, overcoming FH regulation. This suggests that a balanced FHR-1/FH ratio is crucial to control complement amplification on opsonized surfaces. Consistent with this conceptual framework, we show that the genetic deficiency of FHR-1 or decreased FHR-1 in plasma confers protection against developing C3G and associates with better renal outcome.

CONCLUSIONS

Our findings explain how FHR-1 mutants with duplicated dimerization domains result in predisposition to C3G. They also provide a pathogenic mechanism that may be shared by other diseases, such as IgA nephropathy or age-related macular degeneration, and identify FHR-1 as a potential novel therapeutic target in C3G.

MO976: Recurrence of Immune Complex And Complement-Mediated Membranoproliferative Glomerulonephritis in Kidney Transplantation

BACKGROUND AND AIMS

Membranoproliferative glomerulonephritis (MPGN) represents a histologic pattern of glomerular injury which may be due to several etiologies. Few studies have comprehensively analyzed the recurrence of MPGN according to the current classification system.

METHOD

We collected a multicenter, retrospective cohort of 220 patients with biopsy-proven native kidney disease due to MPGN between 1981 and 2021 in 11 hospitals. Demographic, clinical and histologic parameters of prognostic interest were collected. The main outcomes were time to kidney failure, time to recurrence of MPGN, and disease remission after recurrence.

RESULTS

The study group included 34 complement-mediated and 186 immune complex-mediated MPGN. Eighty-one patients (37%) reached kidney failure in a median follow-up of 79 months. The main predictors of this event were the development of rejection episodes, and disease recurrence. Fifty-four patients (25%) had a disease recurrence in a median of 16 months after kidney transplantation. The incidence of recurrence was higher in patients with dysproteinemia (67%) and complement-mediated MPGN(62%). In the multivariable model, complement-mediated MPGN emerged as a predictor of recurrence. Thirty-three patients reached kidney failure after recurrence. The main determinants of no remission were: early time to recurrence (&lt;15 months), eGFR &lt;30 mL/min/1.73 m2 and serum albumin &lt;3.5 g/dL at the time of recurrence.

CONCLUSION

One-fourth of patients with native kidney disease due to MPGN developed clinical recurrence in the allograft, especially in cases with complement-mediated disease or in those associated with dysproteinemia. The kidney outcomes of disease recurrence with currently available therapies are heterogeneous and thus, more effective and individualized therapies are needed.

Development and validation of a nomogram to predict kidney survival at baseline in patients with C3 glomerulopathy

Background

C3 glomerulopathy is a rare and heterogeneous complement-driven disease. It is often challenging to accurately predict in clinical practice the individual kidney prognosis at baseline. We herein sought to develop and validate a prognostic nomogram to predict long-term kidney survival.

Methods

We conducted a retrospective, multicenter observational cohort study in 35 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases. The dataset was randomly divided into a training group (n = 87) and a validation group (n = 28). The least absolute shrinkage and selection operator (LASSO) regression was used to screen the main predictors of kidney outcome and to build the nomogram. The accuracy of the nomogram was assessed by discrimination and risk calibration in the training and validation sets.

Results

The study group comprised 115 patients, of whom 46 (40%) reached kidney failure in a median follow-up of 49 months (range 24–112). No significant differences were observed in baseline estimated glomerular filtration rate (eGFR), proteinuria or total chronicity score of kidney biopsies, between patients in the training versus those in the validation set. The selected variables by LASSO were eGFR, proteinuria and total chronicity score. Based on a Cox model, a nomogram was developed for the prediction of kidney survival at 1, 2, 5 and 10 years from diagnosis. The C-index of the nomogram was 0.860 (95% confidence interval 0.834–0.887) and calibration plots showed optimal agreement between predicted and observed outcomes.

Conclusions

We constructed and validated a practical nomogram with good discrimination and calibration to predict the risk of kidney failure in C3 glomerulopathy patients at 1, 2, 5 and 10 years.

IgA nephropathy is the most common underlying disease in patients with anticoagulant-related nephropathy

Introduction

Anticoagulant-related nephropathy (ARN) is a relatively novel recognized entity characterized by hematuria-associated acute kidney injury (AKI) in the context of overanticoagulation. Preexisting or underlying kidney disease seems to be a predisposing factor; however, few studies have described histologic findings in patients with ARN. We aimed to evaluate underlying kidney pathology in patients on oral anticoagulation who presented an episode of AKI with hematuria in whom a kidney biopsy was performed.

Methods

Retrospective observational multicenter case study in patients treated with oral anticoagulants who developed macroscopic or intense hematuria followed by AKI. Only patients with available kidney biopsy specimens were included. Histologic findings and clinical data throughout follow-up were analyzed.

Results

A total of 26 patients were included with a median age of 75 years (62–80) and a follow-up period of 10.1 months. Of the patients, 80% were male, and most cases (92%) were on anticoagulation with vitamin K antagonists (VKAs). At admission, median serum creatinine (SCr) level was 4.2 mg/dl (2.8–8.2), median international normalized ratio (INR) 2.4 (1.5–3.4), and 11 patients (42%) required acute dialysis during hospitalization. Kidney biopsy results revealed that all patients except 1 had an underlying nephropathy: IgA nephropathy (IgAN) in 19, probable IgAN in 1, diabetic nephropathy in 3, nephrosclerosis in 1, and idiopathic nodular glomerulosclerosis in 1. At 12 weeks after discharge, only 6 subjects (24%) attained complete kidney recovery whereas 7 (28%) remained on chronic dialysis.

Conclusion

IgAN was the most common underlying kidney disease in our biopsy-proven series of ARN, in which a significant percentage of patients did not achieve kidney function recovery.

The management of membranous nephropathy - an update

In the last decades several important advances have taken place in the understanding of the pathogenesis underlying membranous nephropathy, which have sparked renewed interest in its management. Four landmark trials in membranous nephropathy, and a fifth clinical trial-which was a pilot study-, have been published in the last years. The results from some of these trials have had a significant impact in the recommendations included in the 2021 Kidney Disease: Improving Global Outcomes (KDIGO) Guideline for the Management of Glomerular Diseases, which represent a significant step forward compared to the previous guideline in several aspects such as diagnosis, disease monitoring and treatment strategies. However, considering the rapidly evolving advances in the knowledge of membranous nephropathy and the recent publication of the STARMEN and RI-CYCLO trials, several recommendations contained in the guideline warrant updates. This manuscript provides a perspective of the Immunonephrology Working Group of the European Renal Association (ERA) regarding the management of membranous nephropathy in native kidneys of adult patients.

C3 glomerulopathy associated with monoclonal gammopathy: impact of chronic histologic lesions and beneficial effects of clone-targeted therapies

INTRODUCTION

C3 glomerulopathy associated with monoclonal gammopathy (C3G-MIg) is a rare entity. Herein, we analyzed the clinical and histologic features of a cohort of C3G-MIg patients.

METHODS

Retrospective, multicenter, observational study. Patients diagnosed with C3G-MIg between 1995-2021 were enrolled. All had genetic studies of the alternative complement pathway. The degree of disease activity and chronicity was analyzed using the C3G histologic index. Descriptive statistics and propensity-score matching (PSM) analysis were used to evaluate the main outcome of the study (kidney failure [KF]).

RESULTS

The study group included 23 patients: median age 63 years (IQR 48-70), 57% males. IgG kappa was the most frequent MIg (65%). The diagnosis of C3G-MIg was made in transplanted kidneys in 7 patients (30%). Five (22%) had C3 nephritic factor and 5 (22%) anti-factor H antibodies. One patient carried a pathogenic variant in CFH gene.During a follow-up of 40 months (IQR 14-69), 9 patients (39%) reached KF, and these patients had a significant higher total chronicity score in kidney biopsy. Patients who received clone-targeted therapy had a significant higher survival compared to other management. Those who achieved hematological response had a significant higher kidney survival. Outcome was remarkably poor in kidney transplant recipients, 5 of them (71%) reaching KF.By PSM (adjusting for age, kidney function, proteinuria and chronicity score), no significant differences were observed in kidney survival between C3G patients with/without MIg.

CONCLUSIONS

The C3G histologic index can be used in patients with C3G-MIg to predict kidney prognosis, with higher chronicity scores being associated with worse outcomes. Clone-targeted therapies and the development of hematological response, are associated with better kidney prognosis.

Haemolytic uraemic syndrome associated with pancreatitis: report of four cases and review of the literature

Background

The incidence of acute kidney injury (AKI) in patients with acute pancreatitis ranges from 15% to 40% and is associated with poor prognosis. Haemolytic uraemic syndrome (HUS) in the setting of acute pancreatitis is an uncommon association with fewer than 30 cases reported in the literature.

Methods

A retrospective review of the clinical records at our institution between January 1981 and December 2019 was carried out to identify patients with acute pancreatitis and HUS. Additionally, a literature review was conducted on this topic. The aims of the study were to describe the clinical course and outcomes of patients affected by this condition.

Results

Four cases of HUS following an acute pancreatitis were identified. The mean (±SD) age of the study group was 30 ± 6 years, all of which were males. Excessive alcohol consumption was the main cause of acute pancreatitis in all four patients. HUS with progressive AKI developed in a median interval of 2 days from the onset of pancreatitis (range 1-3 days). All patients required kidney replacement therapy during the course of follow-up. A kidney biopsy was performed in two patients, showing typical thrombotic microangiopathic features. One case was treated with eculizumab, whereas the rest were treated with supportive care and/or plasma exchange. A normalization of haematological parameters and complete recovery of kidney function were observed in all patients at last follow-up, although this improvement was significantly faster in the patient treated with eculizumab.

Conclusions

HUS may infrequently develop in patients with acute pancreatitis. An early identification of this complication is mandatory, and complement blockade with eculizumab may be associated with a faster kidney function recovery.

The Forgotten Antiproteinuric Properties of Diuretics

BACKGROUND

Although diuretics are one of the most widely used drugs by nephrologists, their antiproteinuric properties are not generally taken into consideration.

SUMMARY

Thiazide diuretics have been shown to reduce proteinuria by >35% in several prospective controlled studies, and these values are markedly increased when combined with a low-salt diet. Thiazide-like diuretics (indapamide and chlorthalidone) have shown similar effectiveness. The antiproteinuric effect of mineralocorticoid receptor antagonists (spironolactone, eplerenone, and finerenone) has been clearly established through prospective and controlled studies, and treatment with finerenone reduces the risk of chronic kidney disease progression in type-2 diabetic patients. The efficacy of other diuretics such as amiloride, triamterene, acetazolamide, or loop diuretics has been less explored, but different investigations suggest that they might share the same antiproteinuric properties of other diuretics that should be evaluated through controlled studies. Although the inclusion of sodium-glucose cotransporter-2 inhibitors (SGLT2i) among diuretics is a controversial issue, their renoprotective and cardioprotective properties, confirmed in various landmark trials, constitute a true revolution in the treatment of patients with kidney disease. Recent subanalyses of these trials have shown that the early antiproteinuric effect induced by SGLT2i predicts long-term preservation of kidney function. Key Message: Whether the early reduction in proteinuria induced by diuretics other than finerenone and SGLT2i, as summarized in this review, also translates into long-term renoprotection requires further prospective and observational studies. In any case, it is important for the clinician to be aware of the antiproteinuric properties of drugs so often used in daily clinical practice.

SARS-CoV-2-specific Cell-mediated Immunity in Kidney Transplant Recipients Recovered From COVID-19

BACKGROUND

The magnitude and kinetics of severe acute respiratory syndrome coronavirus 2-specific cell-mediated immunity (SARS-CoV-2-CMI) in kidney transplant (KT) recipients remain largely unknown.

METHODS

We enumerated SARS-CoV-2-specific interferon-γ-producing CD69+ CD4+ and CD8+ T cells at months 4 and 6 from the diagnosis of coronavirus disease 2019 (COVID-19) in 21 KT recipients by intracellular cytokine staining. Overlapping peptides encompassing the SARS-CoV-2 spike (S) glycoprotein N-terminal 1- to 643-amino acid sequence and the membrane protein were used as stimulus. SARS-CoV-2 IgG antibodies targeting the S1 protein were assessed by ELISA at month 6.

RESULTS

Detectable (≥0.1%) SARS-CoV-2-specific CD4+ T-cell response was found in 57.1% and 47.4% of patients at months 4 and 6. Corresponding rates for CD8+ T cells were 19.0% and 42.1%, respectively. Absolute SARS-CoV-2-specific T-cell counts increased from month 4 to month 6 in CD8+ (P = 0.086) but not CD4+ subsets (P = 0.349). Four of 10 patients with any detectable response at month 4 had lost SARS-CoV-2-CMI by month 6, whereas 5 of 9 patients mounted SARS-CoV-2-CMI within this period. All but 2 patients (89.5%) tested positive for SARS-CoV-2 IgG. Patients lacking detectable SARS-CoV-2-specific CD4+ response by month 6 were more likely to be under tacrolimus (100.0% versus 66.7%; P = 0.087) and to have received tocilizumab for the previous COVID-19 episode (40.0% versus 0.0%; P = 0.087).

CONCLUSIONS

Although still exploratory and limited by small sample size, the present study suggests that a substantial proportion of KT recipients exhibited detectable SARS-CoV-2-CMI after 6 months from COVID-19 diagnosis.

MO265LONGITUDINAL CHANGE IN PROTEINURIA AND KIDNEY OUTCOMES IN C3 GLOMERULOPATHY

Background and Aims

The association between a change in proteinuria over time and its impact in kidney prognosis has not been analyzed in C3 glomerulopathy. This study aims to investigate the association between the longitudinal change in proteinuria and the risk of kidney failure.

Method

Retrospective, multicenter observational cohort study in 35 nephrology departments belonging to the GLOSEN group. Patients diagnosed with C3 glomerulopathy between 1995 and 2020 were enrolled. A joint modeling of linear mixed-effects models was applied to assess the underlying trajectory of a repeatedly measured proteinuria, and a Cox model to evaluate the association of this trajectory with the risk of kidney failure.

Results

The study group consisted of 85 patients, 70 C3 glomerulonephritis and 15 dense deposit disease, with a median age of 26 years (range 13–41). During a median follow-up of 42 months, 25 patients reached kidney failure. The longitudinal change in proteinuria showed a strong association with the risk of this outcome, with a doubling of proteinuria levels resulting in a 2.5-fold increase of the risk. A second model showed that a ≥50% proteinuria reduction over time was significantly associated with a lower risk of kidney failure (HR: 0.79; 95%CI:0.56–0.97; p&lt;0.001). This association was also found when the ≥50% proteinuria reduction was observed within the first 6 and 12 months of follow-up.

Conclusion

The longitudinal change in proteinuria is strongly associated with the risk of kidney failure. The change in proteinuria over time can provide clinicians a dynamic prediction of kidney outcomes.

Longitudinal change in proteinuria and kidney outcomes in C3 glomerulopathy

INTRODUCTION

The association between a change in proteinuria over time and its impact in kidney prognosis has not been analyzed in C3 glomerulopathy. This study aims to investigate the association between the longitudinal change in proteinuria and the risk of kidney failure.

METHODS

Retrospective, multicenter observational cohort study in 35 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases (GLOSEN). Patients diagnosed with C3 glomerulopathy between 1995 and 2020 were enrolled. A joint modeling of linear mixed-effects models was applied to assess the underlying trajectory of a repeatedly measured proteinuria, and a Cox model to evaluate the association of this trajectory with the risk of kidney failure.

RESULTS

The study group consisted of 85 patients, 70 C3 glomerulonephritis and 15 dense deposit disease, with a median age of 26 years (range 13-41). During a median follow-up of 42 months, 25 patients reached kidney failure. The longitudinal change in proteinuria showed a strong association with the risk of this outcome, with a doubling of proteinuria levels resulting in a 2.5-fold increase of the risk. A second model showed that a ≥ 50% proteinuria reduction over time was significantly associated with a lower risk of kidney failure (HR: 0.79; 95% CI : 0.56-0.97; p < 0.001). This association was also found when the ≥50% proteinuria reduction was observed within the first 6 and 12 months of follow-up.

CONCLUSION

The longitudinal change in proteinuria is strongly associated with the risk of kidney failure. The change in proteinuria over time can provide clinicians a dynamic prediction of kidney outcomes.

Validation of a Histologic Scoring Index for C3 Glomerulopathy

RATIONALE & OBJECTIVE

A previous study that evaluated associations of kidney biopsy findings with disease progression in patients with C3 glomerulopathy (C3G) proposed a prognostic histologic index (C3G-HI) that has not yet been validated. Our objective was to validate the performance of the C3G-HI in a new patient population.

STUDY DESIGN

Multicenter, retrospective cohort study.

SETTING & PARTICIPANTS

111 patients fulfilling diagnostic criteria of C3G between January 1995 and December 2019, from 33 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases (GLOSEN).

PREDICTORS

Demographic, clinical parameters, C3G-HI total activity score, and the C3G-HI total chronicity score.

OUTCOME

Time to kidney failure.

ANALYTICAL APPROACH

Intraclass correlation coefficients and κ statistic were used to summarize inter-rater reproducibility for assessment of histopathology in kidney biopsies. The nonlinear relationships of risk of kidney failure with the total activity score and total chronicity score were modeled using Cox proportional hazards analysis that incorporated cubic splines.

RESULTS

The study group included 93 patients with C3 glomerulonephritis and 18 with dense-deposit disease. Participants had an overall meanage of 35±22 (SD) years. Forty-eight patients (43%) developed kidney failure after a mean follow-up of 65±27 months. The overall inter-rater reproducibility was very good for the total activity score (intraclass correlation coefficient [ICC]=0.63) and excellent for total chronicity score (ICC=0.89). Baseline estimated glomerular filtration rate (eGFR), 24-hour proteinuria, and treatment with immunosuppression were the main determinants of kidney failure in a model with only clinical variables. Only tubular atrophy and interstitial fibrosis were identified as predictors in a model with histological variables. When the total activity score and total chronicity score were added to the model, only the latter was identified as an independent predictor of kidney failure.

LIMITATIONS

Only a subset of the kidney biopsies was centrally reviewed. Residual confounding.

CONCLUSIONS

We validated the performance of C3G-HI as a predictor of kidney failure in patients with C3G. The total chronicity score was the principal histologic correlate of kidney failure.

Invasive pulmonary aspergillosis associated with COVID-19 in a kidney transplant recipient

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might increase the risk of invasive pulmonary aspergillosis (IPA). Although several case reports and small series have been reported in the general population, scarce information is available regarding coronavirus disease 2019 (COVID-19)-associated IPA in the setting of solid organ transplantation. We describe a case of a kidney transplant recipient with severe COVID-19 that was subsequently diagnosed with probable IPA on the basis of the repeated isolation of Aspergillus fumigatus in sputum cultures, repeatedly increased serum (1 → 3)-β-d-glucan levels, and enlarging cavitary nodules in the CT scan. The evolution was favorable after initiation of isavuconazole and nebulized liposomal amphotericin B combination therapy and the withdrawal of immunosuppression.

The STARMEN trial indicates that alternating treatment with corticosteroids and cyclophosphamide is superior to sequential treatment with tacrolimus and rituximab in primary membranous nephropathy

A cyclical corticosteroid-cyclophosphamide regimen is recommended for patients with primary membranous nephropathy at high risk of progression. We hypothesized that sequential therapy with tacrolimus and rituximab is superior to cyclical alternating treatment with corticosteroids and cyclophosphamide in inducing persistent remission in these patients. This was tested in a randomized, open-label controlled trial of 86 patients with primary membranous nephropathy and persistent nephrotic syndrome after six-months observation and assigned 43 each to receive six-month cyclical treatment with corticosteroid and cyclophosphamide or sequential treatment with tacrolimus (full-dose for six months and tapering for another three months) and rituximab (one gram at month six). The primary outcome was complete or partial remission of nephrotic syndrome at 24 months. This composite outcome occurred in 36 patients (83.7%) in the corticosteroid-cyclophosphamide group and in 25 patients (58.1%) in the tacrolimus-rituximab group (relative risk 1.44; 95% confidence interval 1.08 to 1.92). Complete remission at 24 months occurred in 26 patients (60%) in the corticosteroid-cyclophosphamide group and in 11 patients (26%) in the tacrolimus-rituximab group (2.36; 1.34 to 4.16). Anti-PLA2R titers showed a significant decrease in both groups but the proportion of anti-PLA2R-positive patients who achieved immunological response (depletion of anti-PLA2R antibodies) was significantly higher at three and six months in the corticosteroid-cyclophosphamide group (77% and 92%, respectively), as compared to the tacrolimus-rituximab group (45% and 70%, respectively). Relapses occurred in one patient in the corticosteroid-cyclophosphamide group, and three patients in the tacrolimus-rituximab group. Serious adverse events were similar in both groups. Thus, treatment with corticosteroid-cyclophosphamide induced remission in a significantly greater number of patients with primary membranous nephropathy than tacrolimus-rituximab.

Tocilizumab use in Kidney Transplant Patients with COVID-19

A potential benefit of immunomodulatory agents such as tocilizumab (TCZ) has been reported in patients with coronavirus disease 2019 (COVID-19) and severe pulmonary involvement. However, this therapy has been scarcely studied in kidney transplant (KT) recipients. Herein, we describe the clinical course and outcome of 10 KT patients with severe COVID-19 that were treated with TCZ. Mean age of the study group was 54 ± 10 years (70% females), and 30% of the cases were within 6 months from transplant. Mycophenolate mofetil was discontinued in all cases upon admission, whereas baseline steroids were maintained and tacrolimus dose was reduced. Initial treatment included hydroxychloroquine, antibiotics, and prophylactic anticoagulation. Before treatment with TCZ, 3 patients were receiving high-flow oxygen, 4 patients low-flow oxygen and 1 case non-invasive ventilation. All patients received a single dose of intravenous TCZ within a mean time of 7 ± 4 days since admission. During a median follow-up of 16 days (IQR: 10-29), 7 patients (70%) gradually improved and were finally discharged while three cases (30%) did not exhibited clinical improvement and ultimately died. In conclusion, although treatment with TCZ could be associated with improved clinical outcomes in a subset of KT recipients with COVID-19, further studies are warranted before drawing firm conclusions.

Mycophenolate Mofetil in C3 Glomerulopathy and Pathogenic Drivers of the Disease

BACKGROUND AND OBJECTIVES

C3 glomerulopathy is a complement-mediated disease arising from abnormalities in complement genes and/or antibodies against complement components. Previous studies showed that treatment with corticosteroids plus mycophenolate mofetil (MMF) was associated with improved outcomes, although the genetic profile of these patients was not systematically analyzed. This study aims to analyze the main determinants of disease progression and response to this therapeutic regimen.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a retrospective, multicenter, observational cohort study in 35 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases. Patients diagnosed with C3 glomerulopathy (n=81) or dense deposit disease (n=16) between January 1995 and March 2018 were enrolled. Multivariable and propensity score matching analyses were used to evaluate the association of clinical and genetic factors with response to treatment with corticosteroids and MMF as measured by proportion of patients with disease remission and kidney survival (status free of kidney failure).

RESULTS

The study group comprised 97 patients (84% C3 glomerulopathy, 16% dense deposit disease). Forty-two patients were treated with corticosteroids plus MMF, and this treatment was associated with a higher rate of remission and lower probability of kidney failure (79% and 14%, respectively) compared with patients treated with other immunosuppressives (24% and 59%, respectively), or ecluzimab (33% and 67%, respectively), or conservative management (18% and 65%, respectively). The therapeutic superiority of corticosteroids plus MMF was observed both in patients with complement abnormalities and with autoantibodies. However, patients with pathogenic variants in complement genes only achieved partial remission, whereas complete remissions were common among patients with autoantibody-mediated forms. The main determinant of no remission was baseline proteinuria. Relapses occurred after treatment discontinuation in 33% of the patients who had achieved remission with corticosteroids plus MMF, and a longer treatment length of MMF was associated with a lower risk of relapse.

CONCLUSIONS

The beneficial response to corticosteroids plus MMF treatment in C3 glomerulopathy appears independent of the pathogenic drivers analyzed in this study.

Update on C3 Glomerulopathy: A Complement-Mediated Disease

C3 glomerulopathy (C3G) is a clinicopathologic entity secondary to dysregulation of the alternative complement pathway in plasma and the glomerular microenvironment. The current consensus definition of C3G relies on immunofluorescence staining criteria. However, due to its high clinical variability, these criteria may not be accurate enough in some clinical scenarios. Thus, a new pathogenic classification based on a cluster analysis of clinical, histologic, and genetic data has recently been proposed, which could also help identify patients at higher risk of progression. Several pathogenic abnormalities in complement genes have been described, and the role of autoantibodies in the disease is increasingly recognized, but still the genotype-phenotype correlations in C3G are poorly understood. C3G may be diagnosed in both children and adults. The spectrum of clinical manifestations is wide, although one of the most common clinical presentations is proteinuria with relatively preserved kidney function. In order to standardize the evaluation of kidney biopsies from these patients, a histopathologic index was recently proposed, including both parameters of activity and chronicity. However, this index has not yet been validated in independent cohorts. Currently, no targeted therapies are available in clinical settings for the treatment of C3G, although several new molecules are under investigation. Treatment with corticosteroids plus mycophenolate mofetil has been shown to be associated with improved renal outcomes, as compared to other immunosuppressive regimens. Yet, the main determinants of treatment response with this regimen and the influence of the underlying pathogenic drivers have not been extensively studied. The therapeutic response to eculizumab, an anti-C5 monoclonal antibody, has been shown to be highly heterogeneous. Thus, its current clinical indication in C3G is restricted to rapidly progressive forms of the disease. To summarize, in recent years, several important advances have taken place in the understanding of C3G, but still further studies are warranted to elucidate the best therapeutic strategies that could improve prognosis of this entity.

Acute kidney injury in interstitial nephritis

PURPOSE OF REVIEW

The purpose of this review is to describe the most common causes of acute interstitial nephritis (AIN), the diagnostic work-up and the therapeutic management.

RECENT FINDINGS

Several case series and registries have found an increasing incidence of AIN, especially among older patients. Drug-induced AIN still represents the most common cause. Early withdrawal of the culprit drug together with corticosteroid therapy remain the mainstay of treatment, although recent studies have shown that prolonged treatment beyond 8 weeks does not further improve kidney function recovery.

SUMMARY

AIN is a common cause of acute kidney injury, and therefore, physicians should suspect this entity especially in patients exposed to multiple medications. While immune-allergic reaction to numerous drugs is the most common cause of AIN, other underlying systemic diseases may also be involved, and therefore, every patient should undergo a complete diagnostic evaluation. Kidney biopsy provides the definitive diagnosis of AIN, and certain histologic features may help to identify the underlying condition. In drug-induced AIN, an early discontinuation of the culprit drug is the mainstay of therapy, and unless a rapid recovery of kidney function is observed, a course of glucocorticoid therapy should be initiated.

Recurrent acute interstitial nephritis: what lies beneath

Background

Acute interstitial nephritis (AIN) is an emerging cause of acute kidney disease. While this disease usually follows an acute course, it may occasionally recur, representing a major challenge for the clinician.

Methods

We performed a retrospective, observational cohort study in 13 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases. Patients with biopsy-proven AIN between 1996 and 2018 were included.

Results

The study group consisted of 205 patients with AIN, 22 of which developed recurrent AIN (RAIN) after a median of 111 days from diagnosis. RAIN was due to a surreptitious reintroduction of a previously known implicated drug or toxic in six patients (27%), sarcoidosis in two (9%), Sjögren’s syndrome in three (14%), light-chain-mediated AIN in two (9%) and tubulointerstitial nephritis and uveitis syndrome in two (9%), while in the rest of cases (32%), no precise cause could be identified. Microscopic haematuria was more frequent in patients with underlying systemic diseases. The first RAIN episode was treated with a repeated course of corticosteroids in 21 patients (95%). In six cases (27%), azathioprine and mycophenolate mofetil were added as corticosteroid-sparing agents. During a median follow-up of 30 months, 50 patients (27%) with no recurrences and 12 patients (55%) with RAIN reached Stages 4 and 5 chronic kidney disease (CKD). By multivariable logistic regression analysis, RAIN was independently associated with the risk of reaching Stages 4 and 5 CKD, even after adjusting for potential covariables.

Conclusions

RAIN is infrequent but is associated with poor kidney survival. RAIN should prompt clinicians to search for an underlying aetiology other than drug induced. However, in a large percentage of cases, no precise cause can be identified.

Renal potassium handling in chronic kidney disease: Differences between patients with or wihtout hyperkalemia

INTRODUCTION

Hyperkalemia (HK) is a common electrolyte disorder in chronic kidney disease (CKD), mainly in the advanced stages. A positive potassium balance due to reduced renal excretory capacity is likely the main pathogenic mechanism of HK. Research into the relative role of each pathogenic element in the development of HK in CKD may help to implement more suitable therapies.

OBJECTIVE

To investigate renal potassium handling in advanced CKD patients, and to determine the differences between patients with or without HK.

MATERIAL AND METHODS

Cross-sectional observational study in adult patients with stage 4-5 CKD pre-dialysis. Selection criteria included clinically stable patients and the ability to collect a 24hour urine sample correctly. Blood and urinary biochemical parameters were analysed including sodium and potassium (K). Fractional excretion of K (FEK) and K load relative to glomerular filtration (Ku/GFR) were calculated. HK was defined as a serum K concentration ≥5.5mmol/l.

RESULTS

The study group consisted of 212 patients (mean age 65±14 years, 92 females) with a mean GFR of 15.0±4.2ml/min/1.73m². 63 patients (30%) had HK. Patients with HK had lower mean bicarbonate levels with respect to patients with normal K levels (NK) (20.3±3.1 vs. 22.8±3.2 mEq/l, P<.0001), but no differences were noted in total urinary sodium and K excretion. While mean FEK values were lower in patients with HK (32.1±12.1% vs. 36.4±14.3%, P=.038), Ku/GFR values were significantly greater with respect to the NK subgroup (4.2±1.5 vs. 3.7±1.4 mmol/ml/min, P=0,049). FEK showed a strong linear correlation with Ku/GFR (R²=0.74), and partial linear regressions demonstrated that at a similar Ku/GFR level, the FEK of patients with HK was lower than that of NK patients. By multivariate linear and logistic regression analyses, both FEK and Ku/GFR were shown to be the main determinants of K serum levels and HK.

CONCLUSIONS

Although the K load relative to glomerular filtration (Ku/GFR) is an important determinant of HK in advanced CKD, the most noteworthy characteristic associated with HK in these patients was the limitation of compensatory urinary K excretion, as indicated by lower FEK.

IgA Nephropathy in Elderly Patients

BACKGROUND AND OBJECTIVES

Some studies suggest that the incidence of IgA nephropathy is increasing in older adults, but there is a lack of information about the epidemiology and behavior of the disease in that age group.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective multicentric study, we analyzed the incidence, forms of presentation, clinical and histologic characteristics, treatments received, and outcomes in a cohort of 151 patients ≥65 years old with biopsy-proven IgA nephropathy diagnosed between 1990 and 2015. The main outcome was a composite end point of kidney replacement therapy or death before kidney replacement therapy.

RESULTS

We found a significant increase in the diagnosis of IgA nephropathy over time from six patients in 1990-1995 to 62 in 2011-2015 (P value for trend =0.03). After asymptomatic urinary abnormalities (84 patients; 55%), AKI was the most common form of presentation (61 patients; 40%). Within the latter, 53 (86%) patients presented with hematuria-related AKI (gross hematuria and tubular necrosis associated with erythrocyte casts as the most important lesions in kidney biopsy), and eight patients presented with crescentic IgA nephropathy. Six (4%) patients presented with nephrotic syndrome. Among hematuria-related AKI, 18 (34%) patients were receiving oral anticoagulants, and this proportion rose to 42% among the 34 patients older than 72 years old who presented with hematuria-related AKI. For the whole cohort, survival rates without the composite end point were 74%, 48%, and 26% at 1, 2, and 5 years, respectively. Age, serum creatinine at presentation, and the degree of interstitial fibrosis in kidney biopsy were risk factors significantly associated with the outcome, whereas treatment with renin-angiotensin-aldosterone blockers was associated with a lower risk. Immunosuppressive treatments were not significantly associated with the outcome.

CONCLUSIONS

The diagnosis of IgA nephropathy among older adults in Spain has progressively increased in recent years, and anticoagulant therapy may be partially responsible for this trend. Prognosis was poor.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_07_16_CJASNPodcast_19_08_.mp3.