The goal of this observational study is to optimize the evaluation formula for the timing of initiating immunosuppressive therapy in primary membranous nephropathy in patients with primary membranous nephropathy. The main question it aims to answer is:When should immunosuppressive therapy be initiated?This study is a retrospective one. Participants will not receive any treatment.

Inclusion Criteria:

• It meets one of the diagnostic criteria for PMN as stipulated in the KDIGO 2021 Clinical Practice Guidelines for the Management of Glomerular Diseases: patients with a clear diagnosis of PMN based on renal biopsy pathology or presenting with nephrotic syndrome and positive anti-PLA2R antibody detection (>14RU/mL), and excluding secondary factors such as tumors, infections, drugs, and systemic autoimmune diseases.

Exclusion Criteria:

• (1) Patients who have received treatment with immunosuppressive medications other than oral prednisolone.

  (2) The time interval between the renal biopsy and the baseline measurement is longer than 3 years.

  (3) Initiate the use of immunosuppressive agents within 1 week after the diagnosis of PMN.

  (4) Participate in the immunosuppressive treatment trial during the follow-up period and be in the intervention group.

Patients who were registered in the Renal Disease Syndrome Multi-center Cohort Network (https://nsn.bjmu.edu.cn/index) and whose medical records were complete, and who met the PMN diagnostic criteria as stipulated in the KDIGO 2021 Clinical Practice Guidelines for the Management of Glomerular Diseases.