Objective: To investigate the prevalence and clinical significance of antiphospholipid antibodies in patients with systemic sclerosis (SSc).
Methods: Autoantibodies against cardiolipin (aCL) and beta2-glycoprotein 1 (beta2-GPI) were detected by enzyme-linked immunoabsorbent assays (ELISAs) in successively hospitalised SSc patients admitted during a 24-month period. These patients were compared to patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA).
Results: 108 SSc patients were included: 61 had limited cutaneous SSc, 47 had the diffuse sub-type, 16 had primitive pulmonary arterial hypertension (PAH) and 34 had digital ulcerations. The control groups consisted of 37 RA and 38 SLE patients. The prevalence of aCL positivity was lower in SSc patients vs SLE patients (14 vs 47%; p < 0.001), lower in RA patients vs SLE patients (19 vs 47%; p < 0.001), and not different in SSc vs RA patients (14 vs 19%; NS). The mean aCL titer was also lower in SSc vs SLE patients (8+/-10 vs 15+/-20; p < 0.001). In SSc patients, positivity for aCL was associated with PAH (p = 0.009) and the aCL titer correlated with that of the von Willebrand antigen factor (r= 0.23; p = 0.045). The prevalence of anti beta2-GPI positive patients (IgG and/or IgM) was 5% in the SSc group, 18% in the SLE group and 5% in the RA group (SLE vs SSc and SLE vs RA; p = 0.005).
Conclusion: We found that the prevalence of antiphospholipid antibodies in SSc patients was low. However, aCL antibodies were associated with PAH and endothelial injury.