Gemella infective endocarditis complicated by crescentic glomerulonephritis with PR3-ANCA positivity: a case report

Objective: We report a case of Gemella infective endocarditis (IE) complicated by crescentic glomerulonephritis (GN) with proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA) positivity and re-evaluate the clinicopathological spectrum of Gemella-associated renal disease. Patient/Methods: A Japanese man in his 80s presented with low-grade fever and progressive renal dysfunction for several weeks. Blood cultures yielded Gemella species and echocardiography demonstrated valvular vegetation consistent with IE. Laboratory tests revealed elevated urinary abnormalities, elevated inflammatory markers, hypocomplementemia, and PR3-ANCA positivity. A renal biopsy was performed to assess rapidly progressive GN. Results: Histopathological examination revealed crescentic GN with pauci-immune immunofluorescence staining. Antimicrobial therapy was initiated for IE, followed by cautious introduction of corticosteroids after confirmation of infection control. PR3-ANCA titers decreased in parallel with improvements in inflammatory marker levels. However, renal function did not recover sufficiently, and the patient required maintenance hemodialysis. Conclusion: This case demonstrates that Gemella IE may be associated with pauci-immune crescentic GN and PR3-ANCA positivity. Indolent infections due to low-virulence organisms may permit sustained immune activation, thereby contributing to diverse renal manifestations. Careful evaluation is required when renal dysfunction complicates infective endocarditis.