A 22-year-old previously healthy man is brought to the emergency department by his mother because of crushing chest pain, nausea, and vomiting for the past 2 hours. The pain is constant and radiates to his left shoulder. Over the past year, he has been admitted to the hospital twice for deep vein thrombosis. He has a history of learning disability and has been held back three grades. The patient is at the 99th percentile for height and the 45th percentile for weight. His pulse is 110/min, respirations are 21/min, and blood pressure is 128/84 mm Hg. His fingers are long and slender, and his arm span exceeds his body height. Electrocardiography shows ST-segment elevation in leads V1 and V2. His serum troponin I concentration is 2.0 ng/mL. Coronary angiography shows 90% occlusion of the proximal left anterior descending artery. Further testing reveals a homozygous mutation in the methylene tetrahydrofolate reductase gene that leads to decreased enzymatic activity. Due to this defect, the patient most likely has impairment converting homocysteine to which of the following?

Question

A 22-year-old previously healthy man is brought to the emergency department by his mother because of crushing chest pain, nausea, and vomiting for the past 2 hours. The pain is constant and radiates to his left shoulder. Over the past year, he has been admitted to the hospital twice for deep vein thrombosis. He has a history of learning disability and has been held back three grades. The patient is at the 99th percentile for height and the 45th percentile for weight. His pulse is 110/min, respirations are 21/min, and blood pressure is 128/84 mm Hg. His fingers are long and slender, and his arm span exceeds his body height. Electrocardiography shows ST-segment elevation in leads V1 and V2. His serum troponin I concentration is 2.0 ng/mL. Coronary angiography shows 90% occlusion of the proximal left anterior descending artery. Further testing reveals a homozygous mutation in the methylene tetrahydrofolate reductase gene that leads to decreased enzymatic activity.  Due to this defect, the patient most likely has impairment converting homocysteine to which of the following?

Quizplus · Accepted Answer

Eductional Objective: Elevated levels of plasma homocysteine are an independent risk factor for thrombotic events. Homocysteine can be metabolized to methionine via remethylation or to cystathionine via transsulfuration. Hyperhomocysteinemia is most commonly due to genetic mutations in critical enzymes or deficiencies of vitamin B₁₂, vitamin B₆, and folate.

A 22-Year-Old Previously Healthy Man Is Brought to the Emergency