Infective endocarditis presenting as ANCA-associated glomerulonephritis: a complex diagnostic challenge.

A 59-year-old woman with a history of permanent pacemaker placement, prior stroke, and deep vein thrombosis presented with persistent purpuric lesions, lower extremity edema, and acute kidney injury. Laboratory evaluation revealed hemolytic anemia, thrombocytopenia, and myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA) positivity, initially suggesting ANCA-associated vasculitis. Although she received high-dose corticosteroids and a single intravenous dose of cyclophosphamide, the subsequent development of fever and splenic infarction led to a workup revealing Enterococcus faecalis bacteremia and echodensities on the pacemaker leads consistent with infective endocarditis (IE). Renal biopsy demonstrated crescentic glomerulonephritis with fibrinoid necrosis and subepithelial deposits, indicating both ANCA-mediated and immune complex mechanisms. Removal of infected hardware and targeted antibiotic therapy ultimately resolved her infection, improved renal function, and cleared the purpuric lesions. This case highlights the clinical overlap between infective endocarditis and ANCA-associated vasculitis, emphasizing the importance of timely infection screening in patients presenting with rapidly progressive glomerulonephritis and ANCA positivity.