The persistence of serum-specific anti-chikungunya IgM antibodies (CHIKV-IgM) can vary after chikungunya fever (CHIK) infection. However, the factors related to its production are not yet known. We described a case series drawn up from data collected from 57 patients between 12 and 36 months after the acute phase of CHIK infection in Northeastern Brazil. CHIKV-IgM was detectable in 7/57 (12.3%) patients after 28.3 months of infection. No frequency differences in chronic musculoskeletal manifestations and underlying conditions were detected between patients with or without CHIKV-IgM. CHIKV-IgM was detected for up to 35 months in Brazilian patients after CHIK infection.

Introduction Chikungunya virus was detected in cases of acute chikungunya fever in renal tissue. However, chikungunya virus-related kidney injury still lacks characterization, and it is unknown whether the kidneys are reservoirs for the virus. We sought to detect histopathological changes and viral antigens in renal tissue, and to evaluate kidney injury markers in different phases of chikungunya fever. Methods Two groups were evaluated in this exploratory study: patients with biopsy-proven kidney injury established after chikungunya fever, and patients with post-chikungunya fever chronic joint manifestations without known kidney injury, in whom we actively searched for kidney injury markers. Results In the first group, 15 patients had kidney injury 0.5–24 months after chikungunya fever. The most frequent histopathological diagnoses were glomerular lesions. No viral antigens were detected in renal tissue. High-risk genotypes were detected in patients with atypical hemolytic uremic syndrome and focal and segmental glomerulosclerosis. In the second group, 114 patients had post-chikungunya fever joint manifestations on average for 35.6 months. Mean creatinine and proteinuria were 0.9 mg/dl and 71.5 mg/day, respectively. One patient had isolated hematuria. There was no indication for renal biopsy in this group. Conclusions Several histopathological features were found after chikungunya fever, without virus detection in renal tissue. These findings suggest that chikungunya virus may trigger kidney lesions with varying degrees of severity at different stages of infection. However, the probability that this virus replicates in the renal tissue seems unlikely. Graphical abstract

Background: Idiopathic membranous nephropathy (IMN) has been linked to the lectin pathway, IgG4 and genetic susceptibility. We investigated the frequency of mannose-binding lectin2 (MBL2) gene polymorphisms and the serum ratio of IgG4 in patients with membranous nephropathy (MN). Methods: Polymorphisms in the exon 1 of the MBL2 gene (codons 52, 54, and 57) and single base polymorphisms at positions –550 (HL) and –221 (XY) in the promoter region were evaluated in 60 patients compared to a control group (CG) of 101 blood donors. It established the frequency of polymorphisms and the serum ratio of IgG4 comparing 2 etiologies of MN: idiopathic (35 patients) and secondary to systemic lupus erythematosus (25 patients). Results: Patients with MN had a 2.54-fold higher probability (95% CI 1.51–4.31) of carrying the O alelle, exon 1 variant, and 11.16-fold higher probability (95% CI 4.77–28.41) of having A/O genotype when compared to CG. The frequency of polymorphisms in the promoter region was similar between the groups. Combined genotypes generally related to the defective production of MBL (YA/O, XA/O and O/O) were more frequent in patients with MN (OR 7.11; 95% CI 2.69–21.27), when compared to controls. The median of serum ratio IgG4 was 5% for idiopathic MN and 3% for lupus MN patients (p = 0.016). Conclusions: Our data suggests that MBL2 polymorphisms may be associated with the activation of the lectin pathway by IgG4 subclass antibodies in MN.

Introduction: The International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification of lupus nephritis (LN) divides class IV into segmental and global (IV-S and IV-G) based on evidence suggesting different renal outcomes. However, subsequent studies have shown conflicting results. Objective: This study was performed to compare long-term renal outcomes between the IV-S and IV-G classes. Methods: This is a retrospective cohort study of adult patients with biopsy-proven class IV LN using the ISN/RPS classification. The primary end point was end-stage renal disease (ESRD). Results: Among the 89 patients, rapidly progressive glomerulonephritis was twice as frequent in the IV-G group (60 vs. 29%; p = 0.005) than that in the IV-S group. Moreover, the IV-G group had a higher rate of biopsy with cellular and fibrocellular crescents (70.9 vs. 47.1%, p = 0.024) and more crescentic glomerulonephritis (34.5 vs. 5.8%, p = 0.007) than the IV-S group. After a mean follow-up of 57 months, the IV-G group had a greater risk of ESRD (RR 3.9; 95% CI 1.2–12.2, p = 0.006) than the IV-S group. Multivariate analysis indicated that class IV-G was an independent predictor of ESRD. Conclusions: Patients with class IV-G have a higher risk of ESRD than patients with class IV-S.

Aim: Collapsing glomerulopathy (CG) is a glomerular disease that progresses rapidly to renal replacement therapy (RRT). Brazil is a conducive site for studies on CG because of its significant burden of infectious diseases and a high frequency of APOL1 risk variants. We described the clinical characteristics, histopathological findings, and outcomes of CG patients. Methods: This retrospective survey analysed data from 2014 to 2022 from 18 centres of nephrology in all Brazilian regions. CG was diagnosed by kidney biopsy (KB), and the data were collected from medical records: initial symptoms, treatment, evolution to RRT. Results: A total of 330 patients were included. Most patients were men (61.2%) and of Brown/Black ethnicity (72.7%). The mean age was 32 years. The most common symptoms were loss of renal function (44.2%), nephrotic proteinuria (80.07%), and hematuria (52.31%). KB revealed mild tubular atrophy and interstitial fibrosis (53.3%), moderate‐to‐severe interstitial inflammation (35.9%), and acute tubular necrosis (19.0%). On immunofluorescence, IgM (75.5%) and C3 (81.2%) were found to be most frequently deposited. Secondary etiologies were identified in 94 patients: HIV (13.8%), autoimmune disease (15.9%), and APOL1 high‐risk genotype (48.6%, 35/72). The mean follow‐up period was 13 months. Nephrotic proteinuria persisted in 78.8% of patients, and 30.5% progressed to RRT within 3 months after diagnosis. Conclusion: CG affects young patients, leading to RRT in one‐third of cases in approximately 3 months. This multicentre study sets the baselines for risk factors and outcomes in the largest population studies on CG.