RÉSUMÉ
Background: Kawasaki disease (KD) is a paediatric multi-system vasculitis. Mainly, the coronary arteries become affected due to acute inflammation and formation of coronary artery aneurysms (CAAs) may occur. As the size of the CAA increases, so does the risk of clinical complications and serious cardiac outcomes. These patients may experience life-threatening thrombotic coronary artery occlusion and myocardial ischaemia unless antiplatelet and anticoagulation therapy is not initiated in a timely manner.1. Case summary: This case report presents a 12-year-old patient with KD who developed CAAs in two coronary arteries despite initial administration of intravenous immunoglobulins and acetylsalicylic acid, followed by extensive thrombosis of both coronary arteries, although antithrombotic therapy was started after the diagnosis of CAAs. Discussion: Our case is notable because of the severity of the clinical manifestation despite the administration of antiplatelet agents and anticoagulants. It could be speculated that the development of coronary thrombosis in this case might be strongly correlated with the late initiation of oral anticoagulation. The high-quality images of the affected coronary arteries in such a young patient could be of educational value.