We report a case of myocardial infarction at a young age in a subject heterozygous for the G20210A prothrombin gene variant and homozygous for the C677T MTHFR polymorphism, who presented a strong family history of atherothrombosis. Genetic screening for inherited thrombophilia, especially in the presence of a strong familiarity, may be a critical information for secondary prevention of arterial thrombosis.