Is 5-fluorouracil-induced vasospasm a Kounis syndrome? A diagnostic challenge

Cardiovascular hypersensitivity is a rare and well-documented side-effect of 5-FU (5-fluorouracil). Besides the common complications such as angina pectoris and myocardial infarction, it can also cause cardiogenic shock, and supraventricular and ventricular arrhythmias. Studies have reported that FU-induced angina most commonly occurred due to vasospasm. In our case, 9 hours after stopping the infusion of 5-FU, the patients developed symptoms and electrocardiographic (ECG) findings consistent with acute myocardial infarction. We intend to share this rare case and discuss whether this late complication after 5-FU infusion is an FU-induced vasospasm or rather an allergic reaction leading to Kounis syndrome.