BACKGROUND: The metabolic syndrome (MetS) is a proatherogenic entity. Autoantibodies to phospholipid cofactors such as beta2-glycoprotein I (beta2-gpI) can influence atheroma appearance. Previous studies confirmed an association of IgA anti-beta2-gpI antibodies with cerebral ischemia, myocardial infarction, peripheral artery disease and carotid disease. OBJECTIVE: This case-control study evaluates a possible association of anti-beta2-gpI and anticardiolipin (aCL) antibodies with non-complicated MetS. METHODS: Cases comprised patients with MetS without history of vascular events; controls included individuals from the Orthopedic Infirmary admitted due to musculoskeletal disorders. Age, sex, race, history of hypertension, smoking, hypercholesterolemia and diabetes mellitus were evaluated as risk factors in both groups. IgG, IgM, and IgA anti-beta2-gpI and aCL antibodies were detected by enzymatic immunoassay. RESULTS: Sixty-eight patients with MetS and 82 controls were studied. Patients with MetS showed mean age higher than controls (P = 0.001), while males (P = 0.003; OR 0.31; 95%CI 0.15-0.16) and Caucasian ethnicity (P = 0.004; OR 0.25; 95%CI 0.10-0.60) predominated in controls. History of hypertension, hypercholesterolemia and diabetes mellitus were more prevalent in cases than in controls (P < 0.05). The frequency of aCL antibodies (all isotypes) and of IgG and IgM anti-beta2 gpI did not significantly differ in cases and controls. IgA anti-beta2-gpI antibodies were significantly more frequent in MetS patients (42.2%) than controls (10.9%) (P < 0.001). The adjusted OR for IgA anti-beta2-gpI antibodies was 3.60 (95%CI 1.55-8.37; P = 0.003). CONCLUSION: The current study shows that elevated levels of IgA autoantibodies to ß2-gpI might be independently associated to MetS.