Hyperhomocysteinemia is common in patients with antiphospholipid syndrome and may contribute to expression of major thrombotic events.

Homocysteine plasma levels were measured by high-performance liquid chromatography in 52 patients with primary antiphospholipid syndrome (APS). Elevated homocysteine concentrations (>or= 15 micromol/l) were found in 16/52 (30.8%) APS patients. Elevated homocysteine levels were found to be associated with an increased risk for a major thromboembolic event (50 versus 16.7%, P = 0.014). Hyperhomocysteinemia is a common finding in APS patients, and may contribute to severity of thrombotic tendency observed in this syndrome.