Immunopathological Analysis in a French National Cohort of Membranous Nephropathy

Membranous nephropathy is a rare auto-immune disease, yet a major cause of nephrotic syndrome in adults. It is characterised by the deposition of antigen-antibody complexes on the glomerular basement membrane, leading to a decreased filtration rate and eventually kidney failure. About one third of cases have a favourable outcome without any treatment, another third requires a long term symptomatic treatment to manage their symptoms, and the last third of patients advances to end stage renal failure, requiring dialysis and kidney graft. MN can be associated with cancer, infections, other auto-immune diseases and with certain drugs (secondary MN), but most often it is idiopathic. In the latter form two antigens have been identified, PLA2R1 and THSD7A, with corresponding auto-antibodies in 70% and 2% of MN patients, respectively. GWAS studies identified several alleles associated with a higher risk of developing MN, however, since these are common variants they cannot explain the onset of MN in the vast majority of cases. Since MN is a rare disease, the number of new cases per each center is low, and nation-wide studies are needed to correctly evaluate its incidence and risk factors for the onset of MN, as well as validate previously published findings in monocentric studies on the prognostic value of PLA2R1 epitope spreading (immunisation against multiple domains of PLA2R1).

This study aims to establish a French national cohort of all cases of MN in a one year period in France. The inclusion will last one year with one additional year of follow-up, for a total of 2 years. In the first year, nephrologists of each associate centers in France will propose the study to each of their patients diagnosed with MN. In addition, clinical information will be collected, as well as a survey on patients' lifestyle habits. Serum samples will be sent for centralised analyses in Nice.

This study will help to clarify the results from single center studies, such as the prognostic value of epitope spreading. The information acquired on environmental risk factors will help us understand the pathophysiological mechanisms leading to the onset of MN et, by association, to other auto-immune diseases. With this knowledge, measures could be put in place to protect the population at risk.

• Determination of incidence of primary and secondary forms of MN [Time frame: 24 months]
• Identification of environmental factors associated with the onset of MN [Time frame: 24 months]
• Description of the standard of care for patients with MN in France [Time frame: 24 months]
• the prognostic value of epitope spreading in patients with PLA2R1-associated MN [Time frame: 24 months]
• Characterization of HLA typing of MN patients [Time frame: 12 months]
• Prognostic value of tissue staining for glomerular deposit of PLA2R1, THSD7A, as welle as of different IgG subclasses [Time frame: 12 months]