Merck Manual

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Joel L. Moake

, MD, Baylor College of Medicine

Last full review/revision Jan 2021| Content last modified Jan 2021
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Hyperhomocysteinemia may predispose to arterial and venous thrombosis.

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

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

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

The abnormality is established by measuring plasma homocysteine levels in patients with cardiovascular disease or thromboembolism who are suspected of having the disorder.

Treatment of Hyperhomocysteinemia

  • 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.

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