[Homocysteine, a risk factor of atherosclerosis]

Homocysteine is a sulphurated amino acid which, at high plasma concentrations, predisposes to thrombosis and induces focal arteriosclerosis. These characteristics have been established both in patients with homocystinuria, a genetic disease in which homocysteine accumulates in the blood, and in animals submitted to intravenous infusions of this amino acid. Many recent publications have addressed the problem of whether mild increases in plasma homocysteine predisposed to the development of the usual forms of atherosclerosis. Transverse epidemiological studies have established a correlation between homocysteine levels and atherosclerosis at all its vascular localisations, coronary, carotid and lower limb. Multivariate analysis in several prospective studies have shown plasma homocysteine to be an independent risk factor for cerebrovascular accidents and myocardial infarction. Causes of mild increases in plasma homocysteine are usually dietetic deficiencies in folic acid, vitamin B6 or B12, or genetic by mutation of the methylene-tetrahydrofolate reductase. Renal failure is also associated with a high risk in plasma homocysteine levels. However, the toxicity of homocysteine to the arterial wall at slightly elevated concentration remains speculative.