ABCC4 and coronary artery disorder: Platelet overexpression of multidrug resistance protein 4 (MRP4) has been proposed as a molecular mechanism contributing to aspirin low response, and it is a further risk factor for cardiovascular events.<h4>Case summary</h4>An 82-year-old woman with a history of coronary artery disease presented with ST-elevation myocardial infarction 10 days after de-escalation from dual antiplatelet therapy (aspirin plus clopidogrel) to aspirin monotherapy.