Anterior ST-Segment Elevation Myocardial Infarction Followed by Acute Popliteal Artery Occlusion in a 25-Year-Old Tobacco Smoker with Cannabis Use.

Myocardial infarction before 30 years of age warrants evaluation beyond conventional atherosclerosis, particularly when a second arterial event occurs in another vascular bed. A 25-year-old man with a nine-pack-year history of tobacco smoking and occasional cannabis use presented with anterior ST-segment elevation myocardial infarction and underwent primary percutaneous coronary intervention of the left anterior descending artery. Left ventricular ejection fraction was 30%, with severe apical wall-motion abnormality. Twelve days after discharge, he developed acute left popliteal artery occlusion (Rutherford IIb), which improved to IIa and subsequently to I during therapeutic anticoagulation and was managed without revascularization. Fasting homocysteine measured on day 21 was 18.4 µmol/L, with a vitamin B12 level of 121 pg/mL and a folate level of 1.9 ng/mL. Vitamin B12 replacement and folic acid 5 mg/day were prescribed; fasting homocysteine remained mildly elevated at approximately 6 and 18 months (21.6 and 20.7 µmol/L, respectively), with follow-up folate levels of 5.2 and 4.7 ng/mL. Renal and thyroid function were not reassessed at these later measurements. Genotyping showed compound heterozygosity for MTHFR C677T (Methylenetetrahydrofolate reductase) and A1298C, which was considered an accompanying finding rather than a causal thrombophilia. A missed or transient left ventricular apical thrombus represents a plausible, and possibly the most likely, explanation for the limb event. The patient remained free of recurrent thrombotic or bleeding events for 18 months while receiving an individualized warfarin regimen.