Mitral valve vegetations in an elderly patient with acute myeloid leukemia: navigating the overlap between infection and malignancy: a case report.

BACKGROUND: Acute myeloid leukemia (AML) is a hematologic malignancy that can rarely manifest with clinical features resembling infective endocarditis (IE), particularly in elderly individuals. Non-bacterial thrombotic endocarditis (NBTE), a paraneoplastic complication, may present with sterile cardiac vegetations and systemic embolic events, posing significant diagnostic challenges. CASE PRESENTATION: We report the case of an 82-year-old Syrian Arab woman who presented with fever, generalized fatigue, and confusion. Transthoracic echocardiography revealed vegetations on the mitral valve, raising suspicion for IE. However, repeated blood cultures remained negative, and inflammatory markers were only mildly elevated. Laboratory investigations showed marked leukocytosis, anemia, and thrombocytopenia. Peripheral blood smear demonstrated circulating myeloblasts, and flow cytometry confirmed a diagnosis of AML. The presence of sterile vegetations, progressive leukocytosis, and absence of microbiologic evidence supported a diagnosis of NBTE as a paraneoplastic manifestation of AML. CONCLUSION: This case illustrates the importance of considering hematologic malignancies in the differential diagnosis of culture-negative endocarditis. NBTE should be suspected in patients with cardiac vegetations, systemic embolic signs, and unexplained leukocytosis, particularly when blood cultures are repeatedly sterile. Early recognition of this rare presentation is essential for initiating appropriate hematologic evaluation and management.