Glomerulonephritis Associated with Infective Endocarditis Showing Serological Positivity for PR3-anti-neutrophil Cytoplasmic Antibody and Anti-glomerular Basement Membrane Antibody

We herein report a case of crescentic glomerulonephritis (GN) associated with infective endocarditis (IE). A 61-year-old-woman presented with a fever and renal dysfunction and was diagnosed with IE. The patient was positive for proteinase 3-anti-neutrophil cytoplasmic antibody (PR3-ANCA) and anti-glomerular basement membrane (GBM) antibodies. Renal biopsy findings showed crescentic GN with isolated deposition of C3c, a serum conversion product of complement C3. Given these clinical findings, the patient was diagnosed with infective endocardis (IE)-associated GN. Antibiotic therapy was continued without immunosuppressive agents. After the initiation of the antibiotics, the fever resolved, and the renal function gradually recovered. This case highlights the notion that laboratory findings should be carefully evaluated with reference to other findings.