We report a case of myocardial infarction at a young age in a person with a medical history of repeated thrombophlebitis, who was heterozygous for the prothrombin G20210A mutation and homozygous for factor V Leiden mutation. A coronary angiography revealed the presence of a moderate atherosclerotic plaque (60%) in the left anterior descending coronary artery, which gave rise to suspicion of a relationship between prothrombotic gene mutations and atherosclerosis. Genetic screening for inherited thrombophilia, especially in the presence of a strong familiarity or previous venous thrombosis, and the evaluation of atherosclerotic risk factors, may be critical information for primary prevention of arterial thrombosis.