Background <p>Dupilumab, a human monoclonal immunoglobulin G (IgG) antibody that targets the IL-4 and IL-13 receptors, is used to treat various allergic diseases. Several cases of dupilumab-associated autoimmune diseases have been reported in recent years, however, there have been no reports of anti-glomerular basement membrane (GBM) nephritis.</p> Case presentation <p>A 54-year-old woman had been receiving treatment for eosinophilic granulomatosis with polyangiitis (EGPA) since the age of 31. At the age of 51, due to worsening asthma symptoms and eosinophilic sinusitis, treatment with dupilumab was initiated. She was later admitted to the hospital with fever and rapidly progressive kidney dysfunction. Glucocorticoid therapy was started because the possibility of recurrence of EGPA was considered. However, her kidney dysfunction progressed without response, and she was transferred to our hospital. Laboratory tests on admission showed positive anti-GBM antibodies, and a kidney biopsy showed crescentic glomerulonephritis with linear IgG deposition along the GBM without findings suggesting the recurrence of EGPA, including eosinophilic infiltration, granuloma formation, or necrotizing vasculitis. Based on her laboratory data and kidney pathological findings, anti-GBM nephritis was diagnosed. Plasma exchange was performed a total of seven times. Although the anti-GBM antibody titer was decreased after the plasma exchanges, kidney function did not improve well. After additional treatment with intravenous cyclophosphamide, her kidney function improved, and she was discharged home.</p> Conclusion <p>Anti-GBM nephritis associated with EGPA is extremely rare, and dupilumab may have contributed to its development. In patients receiving dupilumab who develop rapidly progressive kidney dysfunction, the possibility of anti-GBM nephritis should be considered, and prompt diagnosis and therapeutic intervention are essential.</p>