Abstract
Abstract Background Kawasaki disease (KD) is a rare paediatric condition that can lead to giant coronary aneurysms. Follow-up of such complex coronary lesions remains a challenge, and their management is difficult to standardize. Case summary Our present case concerns a 17-year-old boy who suffered a giant aneurysm of the left coronary artery, complicated by an asymptomatic stenosis. During regular follow-up, his annual cardiopulmonary exercise test revealed signs of ischaemia (ST depression and premature ventricular complexes). After several further stress tests with inconsistent results, he underwent invasive coronary angiography that revealed significant stenosis with a positive fractional flow reserve (FFR). Discussion We discuss the challenges of diagnosing and managing coronary artery stenosis in paediatric patients with KD, particularly in cases with calcified and thrombosed lesions. A multimodal approach is crucial, including non-invasive imaging, and coronary angiography with optical coherence tomography and FFR. The evaluation of the lesion and its follow-up is an important factor in anticipating the best therapeutic choice for each patient.