New-Onset and Relapsed Membranous Nephropathy post SARS-CoV-2 and COVID-19 Vaccination.

Since the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak and COVID-19 vaccination, new-onset and relapsed clinical cases of membranous nephropathy (MN) have been reported. However, their clinical characteristics and pathogenesis remained unclear. In this article, we collected five cases of MN associated with SARS-CoV-2 infection and 37 related to COVID-19 vaccination. Of these five cases, four (4/5, 80%) had acute kidney injury (AKI) at disease onset. Phospholipase A2 receptor (PLA2R) in kidney tissue was negative in three (3/5, 60%) patients, and no deposition of virus particles was measured among all patients. Conventional immunosuppressive drugs could induce disease remission. The underlying pathogenesis included the subepithelial deposition of viral antigens and aberrant immune response. New-onset and relapsed MN after COVID-19 vaccination generally occurred within two weeks after the second dose of vaccine. Almost 27% of patients (10/37) suffered from AKI. In total, 11 of 14 cases showed positive for PLA2R, and 20 of 26 (76.9%) presented with an elevated serum phospholipase A2 receptor antibody (PLA2R-Ab), in which 8 cases exceeded 50 RU/mL. Conventional immunosuppressive medications combined with rituximab were found more beneficial to disease remission for relapsed patients. In contrast, new-onset patients responded to conservative treatment. Overall, most patients (24/37, 64.9%) had a favorable prognosis. Cross immunity and enhanced immune response might contribute to explaining the mechanisms of MN post COVID-19 vaccination.