Abstract
BACKGROUND: Factor V Leiden is classically linked to venous thrombosis, however arterial events in carriers are uncommon and usually context dependent. CASE SUMMARY: We describe a 39-year-old man with known Factor V Leiden who presented with central chest pain and an inferior ST elevation myocardial infarction. Angiography showed an ectatic right coronary artery with total proximal in stent occlusion and thrombus in the posterior descending artery, and he underwent percutaneous coronary intervention with glycoprotein IIb/IIIa inhibition and heparin. He re-presented with in stent thrombosis requiring repeat intervention, and had mildly elevated homocysteine. His history was notable for peripheral arterial disease with a right femoral stent and a previously repaired right femoral aneurysm. He stabilized with antithrombotic therapy and was discharged the same week, with echocardiography demonstrating preserved systolic and diastolic function. DISCUSSION: This case highlights a rare arterial phenotype in a young Factor V Leiden carrier in the setting of aneurysmal and ectatic arterial anatomy and a mild prothrombotic cofactor. Recognition of permissive vascular anatomy and systematic evaluation for additional thrombosis risks are essential to guide secondary prevention. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12959-025-00800-1.