Minimal change disease (MCD) is a major cause of idiopathic nephrotic syndrome (NS), characterized by intense proteinuria leading to edema and intravascular volume depletion. In adults, it accounts for approximately 15% of patients with idiopathic NS, reaching a much higher percentage at younger ages, up to 70%–90% in children >1 year of age. In the pediatric setting, a renal biopsy is usually not performed if presentation is typical and the patient responds to therapy with oral prednisone at conventional doses. Therefore, in this setting steroid-sensitive NS can be considered synonymous with MCD. The pathologic hallmark of disease is absence of visible alterations by light microscopy and effacement of foot processes by electron microscopy. Although the cause is unknown and it is likely that different subgroups of disease recognize a different pathogenesis, immunologic dysregulation and modifications of the podocyte are thought to synergize in altering the integrity of the glomerular basement membrane and therefore determining proteinuria. The mainstay of therapy is prednisone, but steroid-sensitive forms frequently relapse and this leads to a percentage of patients requiring second-line steroid-sparing immunosuppression. The outcome is variable, but forms of MCD that respond to steroids usually do not lead to chronic renal damage, whereas forms that are unresponsive to steroids may subsequently reveal themselves as FSGS. However, in a substantial number of patients the disease is recurrent and requires long-term immunosuppression, with significant morbidity because of side effects. Recent therapeutic advances, such as the use of anti-CD20 antibodies, have provided long-term remission off-therapy and suggest new hypotheses for disease pathogenesis.

Rituximab induces nephrotic syndrome (NS) remission in two-thirds of patients with primary membranous nephropathy (MN), even after other treatments have failed. To assess the relationships among treatment effect, circulating nephritogenic anti-phospholipase A₂ receptor (anti-PLA₂R) autoantibodies and genetic polymorphisms predisposing to antibody production we serially monitored 24-hour proteinuria and antibody titer in patients with primary MN and long-lasting NS consenting to rituximab (375 mg/m²) therapy and genetic analyses. Over a median (range) follow-up of 30.8 (6.0–145.4) months, 84 of 132 rituximab-treated patients achieved complete or partial NS remission (primary end point), and 25 relapsed after remission. Outcomes of patients with or without detectable anti-PLA₂R antibodies at baseline were similar. Among the 81 patients with antibodies, lower anti-PLA₂R antibody titer at baseline (P=0.001) and full antibody depletion 6 months post-rituximab (hazard ratio [HR], 7.90; 95% confidence interval [95% CI], 2.54 to 24.60; P<0.001) strongly predicted remission. All 25 complete remissions were preceded by complete anti-PLA₂R antibody depletion. On average, 50% anti-PLA₂R titer reduction preceded equivalent proteinuria reduction by 10 months. Re-emergence of circulating antibodies predicted disease relapse (HR, 6.54; 95% CI, 1.57 to 27.40; P=0.01), whereas initial complete remission protected from the event (HR, 6.63; 95% CI, 2.37 to 18.53; P<0.001). Eighteen patients achieved persistent antibody depletion and complete remission and never relapsed. Outcome was independent of PLA2R1 and HLA-DQA1 polymorphisms and of previous immunosuppressive treatment. Therefore, assessing circulating anti-PLA₂R autoantibodies and proteinuria may help in monitoring disease activity and guiding personalized rituximab therapy in nephrotic patients with primary MN.

Selective depletion of B cells with the mAb rituximab may benefit the autoimmune glomerular disease idiopathic membranous nephropathy (IMN). Here, we describe our experience treating 100 consecutive IMN patients with persistent nephrotic syndrome with rituximab. We defined complete remission as persistent proteinuria <0.3 g/24 h and partial remission as persistent proteinuria 50% reduction in proteinuria from baseline. During a median follow-up of 29 months after rituximab administration, 65 patients achieved complete or partial remission. The median time to remission was 7.1 months. All 24 patients who had at least 4 years of follow-up achieved complete or partial remission. Rates of remission were similar between patients with or without previous immunosuppressive treatment. Four patients died and four progressed to ESRD. Measured GFR increased by a mean 13.2 (SD 19.6) ml/min per 1.73 m² among those who achieved complete remission. Serum albumin significantly increased and albumin fractional clearance decreased among those achieving complete or partial remission. Proteinuria at baseline and the follow-up duration each independently predicted the decline of proteinuria. Furthermore, the magnitude of proteinuria reduction significantly correlated with slower GFR decline (P=0.0001). No treatment-related serious adverse events occurred. In summary, rituximab achieved disease remission and stabilized or improved renal function in a large cohort of high-risk patients with IMN.

The pathogenesis of nephrotic syndrome is unclear. However, the efficacy of rituximab, a B cell–depleting antibody, in nephrotic syndrome suggests a pathogenic role of B cells. In this retrospective study, we determined by flow cytometry levels of B and T cell subpopulations before and after rituximab infusion in 28 pediatric patients with frequently relapsing or steroid–dependent nephrotic syndrome. At baseline, patients had lower median percentages of transitional and mature B cells than age–matched healthy controls (P<0.001). Rituximab induced full depletion of B cells (<1% of lymphocytes). At 1 year, most patients exhibited complete total and mature B cell recovery, whereas memory B cell subsets remained significantly depleted. Total T cell concentration did not change with rituximab, whereas the CD4⁺/CD8⁺ T cell ratio tended to increase. Fourteen patients relapsed within 24 months, with a median follow-up of 11.2 months (interquartile range, 8–17.7 months). We observed no difference at baseline between nonrelapsing and relapsing patients in several clinical parameters and cell subset concentrations. Reconstitution of all memory B cell subpopulations, number of immunosuppressive drugs, and dose of tacrolimus during the last 4 months of follow-up were predictive of relapse in univariate Cox regression analysis. However, only delayed reconstitution of switched memory B cells, independent of immunosuppressive treatment, was protective against relapse in multivariate (P<0.01) and receiver operator characteristic (P<0.01 for percentage of lymphocytes; P=0.02 for absolute count) analyses. Evaluation of switched memory B cell recovery after rituximab may be useful for predicting relapse in patients with nephrotic syndrome.

Guidelines recommend steroid plus cyclical cyclophosphamide (St-Cp) therapy for patients with idiopathic membranous nephropathy at high risk of progression to ESRD. Rituximab (Rtx) may be a safer alternative. In this retrospective, observational cohort study, we compared time to any adverse event (primary outcome); serious or nonserious events; partial and complete remission of the nephrotic syndrome; and a composite of doubling of serum creatinine, ESRD, or death between 100 Rtx-treated patients and 103 patients who received daily St-Cp. We monitored patients with standardized protocols and adjusted for baseline characteristics by Cox regression. Over a median follow-up of 40 months, the Rtxgroup had significantly fewer adverse events than the St-Cpgroup (63 versus 173;P<0.001), both serious (11 versus 46;P<0.001) and nonserious (52 versus 127;P<0.001). Cumulative incidence of any first (35.5% versus 69.0%;P<0.001), serious (16.4% versus 30.2%;P=0.002), or nonserious (23.6% versus 60.8%;P<0.001) event was significantly lower with Rtx. Adjusted hazard ratios (95% confidence intervals) between Rtxand St-Cpgroups were 0.27 (0.16 to 0.44) for any first adverse event, 0.32 (0.15 to 0.68) for serious adverse events, and 0.23 (0.13 to 0.41) for nonserious adverse events. Although the cumulative incidence of partial remission was lower in the Rtxgroup, rates of complete remission and the composite renal end point did not differ significantly between groups. Because of its superior safety profile, we suggest that Rtxmight replace St-Cpas first-line immunosuppressive therapy in patients with idiopathic membranous nephropathy and nephrotic syndrome.

In individuals with type 2 diabetes with abdominal obesity, hyperfiltration is a risk factor for accelerated glomerular filtration rate (GFR) decline and nephropathy. In this academic, single-center, parallel-group, prospective, randomized, open-label, blinded end point trial, consenting patients with type 2 diabetes aged >18 years, with waist circumference >94 (males) or >80 (females) cm, serum creatinine 120 mL/min) than nonhyperfiltering patients and was associated with BMI, waist circumference, blood pressure, heart rate, HbA1c, blood glucose, LDL-to-HDL cholesterol ratio, C-reactive protein, angiotensin II, and albuminuria reduction and with increased glucose disposal rate (measured by hyperinsulinemic-euglycemic clamps). Protein and sodium intake and concomitant treatments were similar between the groups. CR was tolerated well. In patients with type 2 diabetes with abdominal obesity, CR ameliorates glomerular hyperfiltration, insulin sensitivity, and other cardiovascular risk factors, effects that might translate into long-term nephro- and cardioprotection.