A 27 year-old man who presented to the hospital with progressive lower extremity weakness, developed an acute ST elevation myocardial infarction on his second hospital day. Primary angioplasty to the left anterior descending coronary artery was performed. Due to persistent dyspnea, the patient underwent a diagnostic chest computed tomography which confirmed multiple small pulmonary emboli. Laboratory analysis revealed a megaloblastic anemia with a reduced vitamin B12 level and positive titers for antibodies against intrinsic factor, establishing a diagnosis of pernicious anemia. Screening for hypercoaguable markers documented an isolated severely elevated homocysteine levels (105 μmol/l). No other significant risk factors for coronary artery disease including a family history of premature atherosclerosis were identified. This case illustrates the importance of testing for hyperhomocysteinemia as part of a workup for atherothrombotic disease, especially in patients without other significant risk factors. The severity of hyperhomocysteinemia found in our patient is unusual for patients with vitamin B12 malabsorption and raises the question of whether the widely practiced folic acid fortification in the United States may mask or even worsen vitamin B12 deficiency over time, leading to more severe cases of vitamin B12 deficiency and hyperhomocysteinemia than seen in the past.