Rapidly Progressive Lupus Nephritis With Concurrent Anti‐GBM and ANCA Positivity: A Rare Case Report

<b>Background:</b> Rapidly progressive lupus nephritis (LN) with concurrent positivity for anti-glomerular basement membrane (anti-GBM) antibodies and antineutrophil cytoplasmic antibodies (ANCAs) represents an exceptionally rare and severe autoimmune overlap. Early identification and timely intervention are critical to prevent irreversible renal damage. <b>Case Presentation:</b> A 23-year-old woman with systemic lupus erythematosus presented with acute kidney injury, nephrotic-range proteinuria, pancytopenia, and a SLEDAI score of 41. Serologic tests revealed high-titer anti-GBM antibodies and dual ANCA positivity (MPO and PR3) by the ELISA technique. Although the patient experienced mild hemoptysis and a significant drop in hemoglobin, MSCT of pulmonary vasculature and parenchyma did not reveal alveolar hemorrhage or vascular lesions. Due to contraindications to renal biopsy, she was empirically treated with pulse-dose corticosteroids and plasma exchange, followed by oral corticosteroids and mycophenolate mofetil. Anti-GBM antibodies became undetectable after seven sessions. The patient achieved full clinical, biochemical, and renal remission within 2 months. <b>Conclusion:</b> This case highlights the importance of early serologic evaluation and prompt immunosuppressive therapy in rapidly progressive LN with anti-GBM/ANCA overlap, particularly when histopathological confirmation is not feasible.