Concurrent anti-GBM disease and p-ANCA vasculitis presenting as pulmonary–renal syndrome in a patient with chronic kidney disease: a case report

Introduction and importance: The coexistence of anti-glomerular basement membrane (anti-GBM) disease and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis represents a rare autoimmune overlap syndrome that poses significant diagnostic and therapeutic challenges. This dual-positive presentation is particularly uncommon in patients with pre-existing chronic kidney disease (CKD) and offers valuable insight into the complexities of disease overlap and management. Case presentation: We report a 48-year-old woman with known CKD who presented with acute pulmonary–renal syndrome manifesting as dyspnea, productive cough, oliguria, and altered sensorium. Laboratory evaluation revealed markedly elevated serum urea and creatinine, raised inflammatory markers, and dual serologic positivity for anti-GBM and perinuclear ANCA (p-ANCA) antibodies, confirming dual-positive vasculitis. Serologic testing was initiated due to persistent respiratory distress and worsening renal function despite appropriate hemodialysis and empiric antibiotic therapy, prompting evaluation for an underlying autoimmune etiology. Testing was performed within the first 48 h of admission after failure of initial supportive measures to produce clinical improvement. The patient received urgent hemodialysis, high-dose intravenous corticosteroids followed by oral taper, plasmapheresis, and cyclophosphamide. Her neurological and respiratory symptoms improved gradually; however, dialysis dependence persisted due to underlying renal damage. Clinical discussion: Dual-positive anti-GBM and ANCA-associated vasculitis represents an uncommon but clinically significant overlap syndrome. The coexistence of both antibodies complicates diagnosis and management, especially in patients with CKD, where baseline renal dysfunction may mask active disease. Early recognition through serologic testing and prompt initiation of combined immunosuppressive and plasmapheresis therapy are critical to preventing irreversible organ injury. This case reinforces the importance of multidisciplinary management and long-term follow-up to monitor disease activity and prevent relapse. Conclusion: This case highlights the need to consider dual-positive anti-GBM and ANCA-associated vasculitis in patients presenting with unexplained renal deterioration or pulmonary symptoms, even in the context of CKD. Timely diagnosis and individualized immunosuppressive therapy can improve outcomes and reduce irreversible organ damage in this rare overlap syndrome.