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By Joel L. Moake, MD, Professor Emeritus of Medicine; Senior Research Scientist and Associate Director, Baylor College of Medicine; J. W. Cox Laboratory for Biomedical Engineering, Rice University

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Hyperhomocysteinemia may predispose to arterial and venous thrombosis.

Hyperhomocysteinemia may predispose to arterial thrombosis and venous thromboembolism, possibly because of injury to vascular endothelial cells. Some experts believe, however, that there is insufficient evidence definitively to link hyperhomocysteinemia to thrombosis.

Plasma homocysteine levels are elevated 10-fold in homozygous cystathionine beta-synthase deficiency. Milder elevations occur in heterozygous deficiency and in other abnormalities of folate metabolism, including methyltetrahydrofolate dehydrogenase deficiency. The most common causes of hyperhomocysteinemia are acquired deficiencies of

  • Folate

  • Vitamin B12

  • Vitamin B6 (pyridoxine)

Folate deficiency is rare in the Western world due to folate fortification of wheat flour.

The abnormality is established by measuring plasma homocysteine levels.


  • Dietary supplementation

Plasma homocysteine levels may be normalized by dietary supplementation with folate, vitamin B12, or vitamin B6 alone or in combination; however, it is not been shown that this therapy reduces the risk of arterial or venous thrombosis.