Left Atrial Appendage Mimicking Coronary Aneurysm and Thrombus on Echocardiography in a Child with Kawasaki Disease

Background: The left atrial appendage (LAA) is an embryologically distinct structure with anatomical features that may mimic pathological findings on echocardiography. In Kawasaki disease, this resemblance can cause diagnostic confusion with coronary artery aneurysm or thrombus. Clinical presentation: A 7-year-old boy presented with fever lasting more than five days and cervical lymphadenopathy following a viral illness. Kawasaki disease was suspected. Transthoracic echocardiography suggested an abnormality of the left coronary artery with possible thrombus, and the patient was started on aspirin, clopidogrel, and apixaban. Coronary computed tomography angiography demonstrated normal coronary origins, course, and caliber, confirming the suspected lesion to be the LAA. Conclusion: The LAA may course adjacent to the left coronary artery and mimic a coronary aneurysm. Multimodality imaging is essential for accurate diagnosis.