Unveiling Lung Adenocarcinoma: Non-bacterial Thrombotic Endocarditis as the Debut Sign.

Non-bacterial thrombotic endocarditis (NBTE) involves the deposition of fibrin and platelets on heart valves, frequently leading to systemic embolism. The association between NBTE and cancer demands thorough investigation in cases lacking an evident cause. This case report elucidates the clinical course of a nonsmoking woman in her sixties with NBTE linked to pulmonary adenocarcinoma. The patient, who had a history of multiple sclerosis (MS) and was receiving dimethyl fumarate treatment, presented to the emergency department with stroke-like symptoms. Diagnostic challenges arose due to preexisting motor sensory impairment from MS. Initial evaluations revealed hypocapnia and elevated inflammatory markers. Blood cultures were obtained twice, and imaging confirmed pneumonia, left pleural effusion, and chronic pulmonary embolism while excluding acute vascular events or intracranial hemorrhage. The first transthoracic echocardiogram (TTE) indicated no cardiac abnormalities. Treatment encompassed parenteral antibiotics, systemic anticoagulation, and admission to medical floors. Although the initial treatment yielded a positive clinical response, subsequent complications emerged. On the tenth day, the patient required additional interventions, including broad-spectrum antibiotics and supplemental oxygen. A follow-up chest X-ray revealed persistent pneumonia and pleural effusion, and blood cultures upon admission returned negative. A subsequent head MRI confirmed an embolic stroke and displayed evidence of MS progression. Around the twentieth day, empirical treatment for infective endocarditis was initiated, and an 8 mm vegetation on the aortic valve was identified via transesophageal echocardiography (TOE). Acute pulmonary edema prompted a transfer to the intermediate care unit. Further investigations, including left thoracocentesis and CT, unveiled exudate and metastatic lesions in the liver, ilium, and kidney. Unfortunately, on the twenty-fifth day, the patient experienced acute myocardial infarction, right leg ischemia, disseminated intravascular coagulation, and shock. Pleural fluid analysis revealed malignant cells suggestive of lung adenocarcinoma. This case underscores the pivotal role of timely NBTE recognition and the search for malignancy when workup for infective endocarditis and autoimmune panels is negative. Moreover, it emphasizes the significance of vigilant monitoring, particularly in immunocompromised individuals or those with preexisting neurological deficits, especially when new neurological symptoms manifest. These insights significantly contribute to the comprehension of NBTE management and its implications for analogous patient cohorts.