Repeated intra-stent thrombus formation in a patient with acute coronary syndrome due to poor responsiveness to clopidogrel may be associated with cytochrome P-450 2C19*2 polymorphism.

A drug-eluting stent was implanted at the culprit lesion in a 65-year-old man with acute coronary syndrome. Nine days after the procedure, he suffered stent thrombosis, and a bare-metal stent was subsequently implanted. Twelve days after this second procedure, a follow-up angiogram showed a newly emerged thrombus at the site of stent implantation. Although the patient had continued dual anti-platelet therapy with aspirin and clopidogrel since the first procedure, platelet optical aggregation test showed no inhibition of aggregation. Further, genetic analysis revealed him to be homozygous for the CYP2C19*2 polymorphism. This case suggests that the mechanism of stent thrombosis, while multi-factorial, is affected greatly by crossover of poor responsiveness to clopidogrel due to the CYP2C19*2 polymorphism.