Two cases of atypical anti-GBM nephritis following SARS-CoV-2 virus vaccination.

Atypical anti-glomerular basement membrane (GBM) nephritis is a rare autoimmune disease characterized by the linear deposition of immunoglobulin G (IgG) detected in the GBM without circulating anti-GBM antibodies or lung involvement. Atypical anti-GBM disease is distinguished from typical anti-GBM disease in both clinical and pathological features. Herein, we report 2 patients who developed mild proteinuria, hematuria, and elevated serum creatinine levels following coronavirus disease 2019 (COVID-19) vaccination. Renal biopsy found bright linear IgG deposition along the GBM, but anti-GBM antibodies were seronegative. Atypical anti-GBM nephritis was determined. The female patient improved with the treatment of valsartan. For the male patient, serum creatinine levels significantly decreased through two plasma exchange sessions, cyclophosphamide, and glucocorticoid. Atypical and typical anti-GBM nephritis are different clinical entities. They target different antigen epitopes and, therefore, atypical anti-GBM disease is not the early stage of typical anti-GBM disease. In atypical anti-GBM nephritis, monoclonal IgG deposition in the glomeruli is not equal to plasma cell dyscrasias but still needs close monitoring for hematologic diseases. The relationship between the disease and COVID-19 vaccination is uncertain and needs further exploration.