Diagnosing and Treating ANCA-Associated Vasculitis within the COVID-19 Era: A Challenging Case Report

Introduction: Anti-neutrophil cytoplasmic antibody (ANCA)- associated vasculitis (AAV) is a rare group of systemic autoimmune diseases that primarily target small blood vessels. Renal manifestations often present as pauci-immune focal and segmental necrotizing crescentic glomerulonephritis (PI-NCGN), which can progress to acute or chronic kidney failure and multiorgan involvement. It is frequently associated with poor outcomes. We report a case of PR3-positive ANCA-associated vasculitis complicated by rapidly progressive glomerulonephritis, acute kidney injury, and diffuse alveolar hemorrhage during the COVID-19 pandemic. This case highlights the diagnostic challenges of differentiating AAV from conditions associated with SARS-CoV-2 infection, as the clinical and radiological presentations of pulmonary-renal syndromes may overlap. The findings underscore the importance of maintaining a comprehensive differential diagnosis in patients with pulmonary and renal involvement, particularly in the post-COVID-19 era, to ensure timely and accurate management of rare autoimmune conditions such as AAV. Conclusion: ANCA-associated vasculitis (AAV) remains a diagnostic and therapeutic challenge, particularly in the post-COVID-19 era, where overlapping clinical and radiological features with SARS-CoV-2 complications can obscure timely identification. This case highlights the critical importance of maintaining a broad differential diagnosis in patients presenting with pulmonary-renal syndromes to differentiate AAV from more common conditions associated with COVID-19.