Diagnostic performance of glomerular PLA2R and THSD7A antibodies in biopsy confirmed primary membranous nephropathy in South Africans

Non-Full House Membranous Lupus Nephritis Represents a Clinically Distinct Subset

Key Points

Non-full house (NFH) membranous lupus nephritis (MLN) is a minor subset of all MLN cases. Patients with NFH MLN tend to be older when diagnosed with systemic lupus erythematosus, undergo first renal biopsy at an older age, and have fewer extrarenal systemic manifestations. Lower load of C3 glomerular deposits seen in NFH MLN biopsies suggests attenuation of complement-mediated injury, which may have wider systemic implications.

Background

Renal involvement in systemic lupus erythematosus (SLE) is a key predictor of morbidity and mortality. Immunofluorescence (IF) staining of glomeruli is typically positive for IgG, IgA, IgM, C3, and C1q—the full house (FH) pattern. However, a subset of patients with membranous lupus nephritis (MLN) have a Non-FH (NFH) IF pattern more typical of idiopathic membranous nephropathy.

Methods

From a multi-institutional cohort of 113 MLN cases, we identified 29 NFH MLN biopsies. NFH MLN was defined by IF criteria: ≥1+ glomerular capillary loop IgG staining and<1+ IgA, IgM, and C1q. FH MLN was defined as ≥1+ staining for all five antibodies. Intermediate (Int) cases did not meet criteria for FH or NFH. We compared the pathological and clinical characteristics and outcomes among patients with FH, NFH, and Int IF patterns on kidney biopsy.

Results

NFH MLN represents a subset of MLN biopsies (13.4%). Compared with patients with FH MLN, patients with NFH MLN were older at SLE diagnosis (29 versus 22.5 years), had a longer time to initial kidney biopsy (8 versus 3.16 years), and had fewer SLE manifestations (2.5 versus 3.36 involved systems). NFH MLN biopsies showed lower C3 IF intensity (1.16+ versus 2.38+). Int biopsies had findings intermediate between those of NFH and FH groups.

Conclusions

NFH IF pattern defines a small subset of MLN biopsies and appears to be associated with milder clinical manifestations and slower disease progression. Less robust C3 deposition in NFH MLN may suggest a pathophysiology distinct from that of FH MLN.

Epidemiology and Outcomes of Glomerular Diseases in Low- and Middle-Income Countries

Glomerular diseases account for a significant proportion of chronic kidney disease in low-income and middle-income countries (LMICs). The epidemiology of glomerulonephritis is characterized inadequately in LMICs, largely owing to unavailable nephropathology services or uncertainty of the safety of the kidney biopsy procedure. In contrast to high-income countries where IgA nephropathy is the dominant primary glomerular disease, focal segmental glomerulosclerosis is common in large populations across Latin America, Africa, Middle East, and South East Asia, while IgA nephropathy is common in Chinese populations. Despite having a high prevalence of known genetic and viral risk factors that trigger focal segmental glomerulosclerosis, membranoproliferative glomerulonephritis also is common in adults and children in some African countries. Treatment of glomerular diseases in adults and children in LMICs largely is dependent on corticosteroids in combination with other immunosuppressive therapy, which often is cyclophosphamide because of its ready availability and low cost of treatment, despite significant adverse effects. Partial and/or complete remission status reported from studies of glomerular disease subtypes vary across LMIC regions, with high rates of kidney failure, mortality, and disease, and treatment complications often reported. Improving the availability of nephropathology services and ensuring availability of specific therapies are key measures to improving glomerular disease outcomes in LMICs.

Membranous nephropathy: Systems biology-based novel mechanism and traditional Chinese medicine therapy

Membranous nephropathy (MN) is a renal-limited non-inflammatory autoimmune disease in the glomerulus, which is the second or third main cause of end-stage kidney diseases in patients with primary glomerulonephritis. Substantial achievements have increased our understanding of the aetiology and pathogenesis of murine and human MN. The identification of nephritogenic autoantibodies against neutral endopeptidase, phospholipase A₂ receptor (PLA₂R) and thrombospondin type-1 domain-containing 7A (THSD7A) antigens provide more specific concept-driven intervention strategies for treatments by specific B cell-targeting monoclonal antibodies to inhibit antibody production and antibody-antigen immune complex deposition. Furthermore, additional antibody specificities for antigens have been discovered, but their pathogenic effects are uncertain. Although anti-PLA₂R and anti-THSD7A antibodies as a diagnostic marker is widely used in MN patients, many questions including autoimmune response development, antigenic epitopes, and podocyte damage signalling pathways remain unresolved. This review describes the current available evidence regarding both established and novel molecular mechanisms based on systems biology approaches (gut microbiota, long non-coding RNAs, metabolite biomarkers and DNA methylation) in MN, with an emphasis on clinical findings. This review further summarizes the applications of traditional Chinese medicines such as Tripterygium wilfordii and Astragalus membranaceus for MN treatment. Lastly, this review considers how the identification of novel antibodies/antigens and unresolved questions and future challenges reveal the pathogenesis of MN.

Remissions in Patients with Idiopathic Membranous Nephropathy Treated with Rituximab in Senegal

Objectives: This study aimed to evaluate the efficacy of Rituximab in the management of idiopathic membranous nephropathy (IMN) based on the following criteria: (I) Biological remission at three months (M3) and six months (M6); (II) change in mean proteinuria (24PU), mean serum albumin, and mean serum creatinine at M3 and M6; (III) and side effects. Methods: This retrospective descriptive and analytical study included patients with histologically confirmed IMN with positive plasma anti-PLA2R antibodies who received at least one dose of Rituximab after six months of follow-up without spontaneous remission. Patients with unexplainable records were not included. Results: A total of five patients (P1, P2, P3, P4, and P5), including four males and one female were analyzed. The mean age was 44.20 ± 23.14 years. All patients had IMN type 2. At inclusion, the mean albuminemia, mean creatinine, and mean 24hPU levels were 15.56 ± 5.27 g/L, 17.3 ± 7.6 mg/L, and 6.54 ± 1.13 g/24h, respectively. The median anti-PLA2R antibody titer was 100 IU with extremes of 10 and 800 IU. Partial remission was noted in three patients at M3 (P2, P4, and P5), and it was maintained until M6 in P2. No complete remission was observed. A significant decrease in mean 24hPU at M3 was noted (P < 0.001). Generalized pruritus associated with seizures was noticed in P4 after the first dose of Rituximab. Conclusions: Partial remission was noted in three patients at M3, and one patient maintained this remission at M6. Rituximab significantly reduced 24hPU at M3 after administration. Rituximab administration was well tolerated by the patients.