High prevalence of hyperhomocyst(e)inemia in patients with juvenile venous thrombosis.

We determined the prevalence of hyperhomocyst(e)inemia before and 4 hours after a methionine load (3.8 g/m2) in 80 patients (25 mean and 55 women) who had had at least one verified episode of venous thromboembolism before the age of 40 years and in 51 healthy control subjects. No patient had any of the hemostatic abnormalities known to be associated with increased risk of venous thrombosis, and all had normal renal and liver function and no evidence of neoplastic disease. Hyperhomocyst(e)inemia was defined as fasting plasma homocyst(e)ine levels or absolute postload increments of homocyst(e)ine above the normal range. According to these diagnostic criteria, 15 patients (18.8%) and 1 control subject (1.9%) had hyperhomocyst(e)inemia. In 1 of these patients only, hyperhomocyst(e)inemia could be explained by low serum concentrations of vitamin B12 and folates. The family history for venous thromboembolism was positive for 7 of the 15 patients. Family studies, performed for eight kindreds, showed that for more than half of the studied probands the abnormality was inherited. This study indicates that moderate hyperhomocyst(e)inemia is associated with an increased risk of developing venous thromboembolism at a young age and that measurements of fasting and postmethionine plasma homocyst(e)ine levels may be useful in the evaluation of patients with juvenile venous thromboembolism, particularly if their family history suggests the presence of an inherited abnormality.