Rituximab had been shown to be effective in inducing remission of nephrotic syndrome in patients with idiopathic membranous nephropathy (iMN). This study applied rituximab therapy for 36 non-responsive iMN patients to investigate its effects and safety. Thirty-six iMN patients who were non-responsive to prior immunosuppression were enrolled. Rituximab was used for B-cell depletion in patients, with a goal of <5 B cells/mm³ in the circulation. After completing the study, patients were monitored for a median of 12.0 months [interquartile range (IQR) 9.0–19.3]. Fifteen of the 36 (41.7%) patients achieved partial (n = 13) or complete (n = 2) response to the rituximab treatment. The median time for achieving partial response was 4.0 months (IQR 3.0–6.0). The responders had relatively lower levels (118 ± 112 U/mL versus 345 ± 357 U/mL, P = 0.03) of anti-phospholipase 2 receptor (PLA2R) antibodies before the rituximab treatment, and all of them achieved antibody depletion or reduction. B-cell depletion was achieved in all patients. Renal function remained stable in the responders [estimated glomerular filtration rate (eGFR) 53.3 ± 40.5 versus 55.6 ± 33.2 mL/min/1.73 m², P = 0.67] but deteriorated in the non-responders (eGFR 57.5 ± 29.3 versus 45.3 ± 32.8 mL/min/1.73 m², P = 0.02) with two patients reaching end-stage kidney disease. Two of the 15 patients relapsed during the follow-up period with anti-PLA2R antibody reoccurrence and B-cell reconstitution. The second course of rituximab combined with tacrolimus induced a faster partial response again in one patient. Rituximab therapy could induce remission of proteinuria and stabilization of renal function in non-responsive iMN patients, even those with damaged renal function. Anti-PLA2R antibodies may be used as a marker for individualized rituximab dosage and treatment monitoring.

The elderly population has significantly increased in China. However, data regarding renal histopathology in this population is lacking. The present study retrospectively analyzed renal disease spectrum of 430 elderly patients who had received renal biopsy at Peking University First Hospital between January 2003 and December 2012. Among 6049 patients receiving renal biopsies during the same period, 430 (7.10%) were elderly (≥65 years). The ratio of male (263 patients) to female (167 patients) was 1.57:1, with an age of 70.29±3.99 (range 65-82) years at the time of biopsy. The most common indication for renal biopsy was nephrotic syndrome (59.53%), followed by acute kidney injury (AKI, 19.53%) and chronic glomerulonephritis (CGN, 16.05%). The most common renal histopathology in primary glomerular disease was idiopathic membranous nephropathy (iMN, 61.02%), followed by IgA nephropathy (18.22%), minimal change disease (MCD, 9.32%) and focal segmental glomerulosclerosis (6.78%). ANCA-associated vasculitis (AAV, 43.95%) was the leading secondary glomerular disease, followed by HBV-related glomerulonephritis (HBV-GN, 24.2%), and amyloidosis (14.01%). In patients with nephrotic syndrome, iMN (50%) was the leading cause, followed by HBV-GN (16.02%), MCD (7.81%), and amyloidosis (7.81%). In patients with iMN, 89.5% presented as nephrotic syndrome, 8.39% as CGN. In patients with AKI, the leading cause was AAV (48.12%), followed by acute interstitial nephritis (20.48%) and acute tubular necrosis (8.43%). In conclusion, in elderly Chinese patients, the most common renal histopathology pattern was iMN in patients with nephrotic syndrome, and AAV in patients with AKI.

Long-term exposure of mercury may induce glomerulonephritis. Clinical and pathological features of mercury-associated glomerulonephritis are not fully clear. This study retrospectively analyzed 35 cases of mercury-associated glomerulonephritis in a single Chinese center. Thirty-five patients of mercury-associated glomerulonephritis were enrolled. Clinical data on diagnosis and during follow-up were collected. Plasma anti-phospholipase A2 receptor (PLA2R) antibody, glomerular PLA2R and glomerular IgG subclasses deposition were detected in the cases with membranous nephropathy (MN). Mercury exposure was caused by skin lighting cream (20 patients), mercury-containing pills (9 patients), hair-dyeing agents (4 patients), and unidentified reasons (2 patients). All patients presented with proteinuria and normal renal function. The median of urinary protein was 4.6 (range 1.6~19.7) g/24 h. Twenty-two patients (62.9%) had nephrotic syndrome. Renal histopathology showed minimal change disease (MCD) in 21 patients (60.0%), MN in 13 (37.1%) and focal segmental glomerular sclerosis (FSGS) in 1 patient (2.9%). The proportion of MCD increased along with urinary mercury concentration (P = 0.024). In 13 cases of MN, all patients were negative for plasma anti-PLA2R antibody and glomerular PLA2R antigen. IgG1 (61.5%) and IgG4 (46.2%) deposits were noted along the glomerular capillary loops. Among the 16 patients received mercury detoxification monotherapy, 14 patients received 4.5 ± 2.8 (range 1~12) rounds of regimen and achieved complete remission in 4.5 (range 0.3~23.0) months, 2 patients stayed no remission. MCD was the most common pathological type of mercury-associated glomerulonephritis, followed by MN. The proportion of MCD increased along with the increase of urinary mercury concentration. Most patients could achieve complete remission after mercury detoxification.

Monoclonal gammopathy of renal significance (MGRS) is a recently defined group of renal diseases caused by monoclonal immunoglobulin secreted by nonmalignant proliferative B cell or plasma cell. Monoclonal immunoglobulin can form different types of structures deposited in renal tissue, including fibrils, granules, microtubules, crystals and casts, and has mostly been reported in multiple myeloma patients. Here we report a rare case with κ light chain crystals in both podocytes and tubular epithelial cells associated with MGRS, which adds more information to the spectrum of MGRS-related renal diseases. A 53-year old woman presented with albumin–predominant moderate proteinuria and renal failure. She had monoclonal IgGκ in the serum and monoclonal IgGκ plus free κ in the urine. Multiple myeloma and lymphoproliferative disorders were excluded. Renal biopsy confirmed κ-restricted crystal-storing renal disease involving the podocytes and proximal tubular epithelial cells. The patient was treated with bortezomib followed by lenalidomide-based chemotherapy, and renal function was stable after 1 year of follow-up. This is a rare case of combined crystalline podocytopathy and tubulopathy associated with MGRS, in which diagnosis was dependent on electron and immuno-electron microscopy.