Left main coronary artery occlusion is a very rare entity that often results in death. It usually manifests as acute myocardial infarction (MI) with cardiogenic shock and fatal arrhythmias. Here, we report the case of a 19 year-old patient who presented with acute anterior MI secondary to left main coronary artery thrombosis. There were no classical risk factors for coronary heart disease in the anamnesis of the patient. Leukaemia was regarded to be the most probable predisposing condition in the patient.