Hyperhomocysteinemia and venous thrombosis

In recent years hyperhomocysteinemia has been established as a new risk fac tor for neural tube defects, arterial cardiovascular disease, and venous th rombosis. Concerning vascular problems, it first became clear that hyperhom ocysteinemia might be (though not proven) a risk factor for arterial diseas e as observed in case-control studies, as well as in prospective analysis. More recently, the subject of hyperhomocysteinemia and venous thrombosis ha s received much attention. In this article, we discuss the issue of hyperho mocysteinemia, in general, the known causes of hyperhomocysteinemia and the association with venous thrombosis. Special attention is given to the valu e of the methionine loading test to diagnose hyperhomocysteinemia. An assoc iation of venous thrombosis and hyperhomocysteinemia has now been documente d in several case control studies, but only in one prospective analysis. Th us far, there is limited evidence for a causual relationship for mild hyper homocysteinemia in venous thrombosis. Briefly, the possible mechanisms of h ow hyperhomocysteinemia can lead to venous thrombosis are discussed. The ar ticle ends with therapeutic options to treat hyperhomocysteinemia (hyperhom ocysteinemia can easily be treated with vitamins) and the description of a study that is presently being undertaken in an international multicenter de sign. This placebo-controlled study might resolve the question of whether l owering of homocysteine levels is of any clinical relevance in preventing r ecurrent venous thrombosis.