Coagulation
Hereditary thrombophilia / hypercoagulopathies
Hyperhomocysteinemia
Author: Jeremy C. Parsons, M.D.
Last author update: 1 June 2012
Last staff update: 22 September 2020
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Hyperhomocysteinemia [title]
Cite this page: Parsons JC. Hyperhomocysteinemia . PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationhyperhomocysteinemia.html. Accessed December 23rd, 2024.
Definition / general
- Homocysteine is an amino acid, derived from methionine, may be converted to cysteine
- Its metabolic pathways require vitamins B12, B6 and folate
- Elevated levels may be hereditary (due to mutations in these pathways) or acquired (due to deficiencies of vitamins B12, B6 or folate, renal failure, carcinoma, hypothyroidism or medications)
- Elevations in homocysteine are associated with increased risk of arterial and venous thrombosis and atherosclerosis, based on retrospective case control studies
- Prospective studies show a weak positive association with arterial thrombosis, and no definite association for venous thrombosis
- Homozygosity or heterozygosity for the C677T mutation in MTHFR gene (methylene tetrahydrofolate reductase), which is involved in homocysteine metabolic pathway, does not appear to be a risk factor for thrombosis, but may be significant in folate - deficient patients
- Although MTHFR was previously thought to be associated with thrombosis, newer data suggests this test is not useful in the first - line evaluation of thrombosis
- Mutation in the methioninesynthetase gene (MTR) also can lead to increased homocystein levels but, as with MTHFR mutations, are not thought to be associated with thrombosis
- Consider testing patients with documented coronary artery disease, cerebrovascular disease or peripheral vascular disease for homocysteine
- High levels can be treated with vitamins B6, B12, folic acid, trimethylglycine, although they may not reduce the risk of future cardiovascular events
- Homocysteinemia is usually associated with a moderately elevated plasma homocysteine, while homocysteinuria is a specific genetic entity with very high plasma homocysteine levels
Diagrams / tables
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Folate metabolism
Additional references
