Delayed Diagnosis of Non-Bacterial Thrombotic Endocarditis in a Patient With Metastatic Lung Cancer

Non-bacterial thrombotic endocarditis (NBTE) is characterised by sterile vegetations on cardiac valves and is most frequently associated with malignancy or chronic inflammatory disorders. Diagnosis is challenging, as clinical signs typically manifest after embolic complications. We report the case of a 42-year-old man with a history of myocardial infarction and lacunar stroke earlier in the year, who presented with chronic cough, progressive dyspnoea, and fatigue. On admission, he was tachycardic and tachypneic, with a diastolic murmur and bibasal crackles. Laboratory tests revealed normocytic anaemia and thrombocytopenia. Computed tomography pulmonary angiogram (CTPA) excluded pulmonary embolism but demonstrated a large pericardial effusion, confirmed on transthoracic echocardiography, along with severe aortic regurgitation and a mobile echodensity on the aortic valve suspicious for vegetation. Pericardiocentesis drained 940 mL of haemoserous fluid, and cytology subsequently confirmed metastatic adenocarcinoma of probable pulmonary origin. Further imaging revealed bilateral renal and splenic infarcts. Serial blood cultures were negative. Given the combination of sterile vegetations, systemic embolisation, and advanced malignancy, a diagnosis of NBTE was made. The patient was managed supportively, with surgical intervention deferred in view of disseminated malignancy and poor prognosis. His condition deteriorated rapidly, and he died several days after discharge. This case illustrates the importance of considering NBTE in patients presenting with recurrent embolic events, particularly in the context of malignancy. Prompt recognition and initiation of anticoagulation may reduce the risk of further embolic complications, although prognosis remains poor in cancer-associated NBTE.