Infertility Treatment-Associated Abiotrophia defectiva Endocarditis Mimicking ANCA Vasculitis: A Case Report

We report a rare case of a 41-year-old woman with Abiotrophia defectiva infective endocarditis (IE) after infertility treatment, mimicking ANCA-associated vasculitis. A. defectiva is a nutritionally variant streptococcus found in human microbiota, rarely causing IE. The patient had undergone four unsuccessful oocyte retrieval cycles and discontinued treatment. One week later, she developed lower back pain, night sweats, and persistent cold-like symptoms. Initial blood tests revealed elevated inflammatory markers, anemia, and PR3-ANCA positivity, leading to a misdiagnosis of ANCA-associated vasculitis and treatment with prednisolone. Shortly after, the patient presented with worsening symptoms. Echocardiography revealed mitral valve destruction with severe regurgitation, vegetation, and pericardial effusion. MRI identified cerebellar infarction and subarachnoid hemorrhage. Emergency mitral valve replacement with a bioprosthesis was performed due to extensive valvular destruction. Blood cultures and intraoperative valve cultures confirmed A. defectiva . Preoperative antibiotic therapy included meropenem and vancomycin, which were later de-escalated to ceftriaxone for six weeks. The patient’s recovery was uneventful, normalized inflammatory markers, and PR3-ANCA levels. At 12-month follow-ups, she remained asymptomatic with no evidence of ANCA-associated disease. This case underscores the challenges of diagnosing A. defectiva IE due to overlapping clinical features with ANCA-associated vasculitis .