Hyperhomocysteinemia as a cause of superior vena cava syndrome.

A case is presented in which superior vena cava (SVC) syndrome was caused by a stenosis of the SVC due to thrombosis. Hyperhomocysteinemia was diagnosed as a possible underlying mechanism. The role of hyperhomocysteinemia as a risk factor for the development of recurrent venous thrombosis, its diagnosis, and treatment are discussed.