Background: Infective endocarditis (IE) is an inflammatory and exudative disease that primarily affects the heart valves. Its diagnosis includes clinical, bacteriological, imaging, and histopathological findings. This condition can induce clinical manifestations associated with systemic vasculitis, with a positive serology for ANCA antibodies. We present the case of an elderly woman with purpura, glomerulonephritis, and positivity for PR3 antibodies, who was diagnosed with endocarditis caused by Bartonella henselae .

Case presentation: 80-year-old woman with history of biological mitral valve replacement in 2019 was admitted due to a syncopal episode. She had previously experienced progressive weight loss. Physical examination revealed a grade III systolic murmur at the mitral focus and palpable purpura in the lower limbs. Laboratory tests showed anemia, thrombocytopenia, renal impairment with hematuria and proteinuria. The initial echocardiogram and blood cultures were unremarkable. Suspecting an immune-mediated disorder, autoimmune tests were performed, revealing positive ANA 1:80 with a reticular cytoplasmic pattern, elevated rheumatoid factor, high titers positive ANCA-PR3, and hypocomplementemia. With these findings, ANCA-associated vasculitis was considered. However, findings from a transesophageal echocardiogram performed to investigate the syncopal episode, documented a 15 mm vegetation in the biological mitral valve prosthesis. Based on this result, infectious studies were expanded, revealing positive IgM and IgG serology for Bartonella henselae . The patient was started on antibiotic therapy with doxycycline and rifampicin for 14 days, and mitral valve replacement was performed. The patient had a favorable outcome, with resolution of all the initial clinical and immunological manifestations.

Learning points for clinical practice: It has been reported that endocarditis of any origin induces ANCA positivity in 19-24% of cases, with this prevalence reaching up to 60% in cases of IE caused by Bartonella ; in this context, PR3 positivity is more common than MPO positivity. Unusually, hypocomplementemia and positive rheumatoid factor may be observed. This case highlights the importance of recognizing Bartonella infection as a potent inducer of small vessel vasculitis with clinical features typical of ANCA-associated vasculitis. Early recognition and timely treatment are essential for achieving favorable outcomes.

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Disclosure of Interests: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.