Background and objectivesC3 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).ResultsThe 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.ConclusionsThe beneficial response to corticosteroids plus MMF treatment in C3 glomerulopathy appears independent of the pathogenic drivers analyzed in this study.

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.

Background IgA nephropathy (IgAN) may recur in kidney transplant recipients. B‐cell‐activating factor (BAFF), a proliferation‐inducing ligand (APRIL), and α‐defensins are involved in the pathogenesis of native IgAN; however, their role on IgAN recurrence has not been previously analyzed. Methods Thirty‐five patients with IgAN who received a kidney transplant in our center between January 1, 1993, and December 31, 2015, were included. Recurrence was diagnosed and ruled out in 14 and 11 patients, respectively, by indication biopsies. Pre‐transplant, 6‐month, 1‐, 3‐, and 5‐year sera selected to measure BAFF, APRIL, and defensin by ELISA. Results Six months post‐transplantation, APRIL levels (300.1 vs 1203.8 pg/mL, P = 0.033) and the mean APRIL values from 6 months to 3 years (409.8 vs 1258.0 pg/mL, P = 0.003) were higher in recurrent patients. Both 6‐month APRIL levels (AUC‐ROC 0.753, P = 0.033) and mean APRIL values (AUC‐ROC 0.844, P = 0.004) discriminated patients with recurrence risk. By logistic regression, APRIL at 6 months (P = 0.044) and mean APRIL (P = 0.021) related to the risk of IgAN recurrence independently. Neither BAFF nor defensin related to recurrence. Conclusions Serum APRIL increased at 6 months and mean APRIL remained higher the first 3 years in patients in whom IgAN was going to recur.

Mycobacterium xenopi is an unusual pathogen and few such cases have been reported in the literature. We report the case of a patient with a sirolimus-based immunosuppressive regimen, who developed lung cavitation. M. xenopi was isolated from the sputum. The patient was treated initially with rifampicin, isoniazid, and pyrazinamide; levofloxacin was added to the treatment regimen after M. xenopi was demonstrated. A possible relationship between sirolimus and M. xenopi infection has been postulated, probably due to the combination of pulmonary toxicity and cellular immunosuppression of rapamycin.