Granulicatella adiacens Endocarditis Mimicking an Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

backgroundInfective endocarditis (IE) can mimic antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, posing diagnostic challenges due to overlapping clinical and serological features. CASE SUMMARY: A 27-year-old man presented with a 3-month history of fatigue, weight loss, fever, petechiae, and peripheral edema. Initial findings suggested ANCA-positive vasculitis, but blood cultures identified Granulicatella adiacens, confirming IE with glomerulonephritis and cutaneous manifestations. Echocardiography revealed severe aortic regurgitation with vegetations. Despite antibiotics, clinical deterioration required urgent valve replacement. The renal function and cutaneous lesions resolved postoperatively, and the patient fully recovered. DISCUSSION: This is the first reported case of G. adiacens IE mimicking ANCA-associated vasculitis. The case highlights the diagnostic complexity of IE in young adults with autoimmune features, emphasizing the need for thorough microbiological evaluation. TAKE-HOME MESSAGES: IE should be considered in ANCA-positive patients with systemic symptoms, even when young and without prior intravenous drug use. Timely diagnosis and treatment are critical to avoid inappropriate immunosuppressive therapy.