Marantic Endocarditis in Malignancy: A Case Report of a Challenging Diagnosis

Marantic endocarditis is a condition characterized by sterile vegetations in the heart valves, and is much rarer than infectious endocarditis. It's typically associated with conditions such as cancer or autoimmune diseases. We report the case of a patient with stage four lung cancer, presenting with fever after chemotherapy, and diagnosed with marantic endocarditis, after extensive testing to exclude an infectious agent. The patient's imaging techniques suggested infectious embolization to the liver and spleen, which supported the diagnostic hypothesis of infectious endocarditis, but the liver biopsy was positive for metastasis. Oncology was consulted for follow-up, and the patient was discharged on anticoagulation therapy, the standard treatment for marantic endocarditis. This case underscores the difficulty of diagnosing marantic endocarditis and the extensive testing required, considering its poor prognosis and the importance of treatment.