To determine the prevalence and clinical significance of antiphospholipid antibodies (aPL) in a cohort of patients with primary Sjögren's syndrome (SS).
Eighty patients with primary SS were studied prospectively. The prevalence of aPL and characteristics of the clinical and laboratory features of these patients were compared with those of the following groups of patients: (i) 50 patients with SS associated with systemic lupus erythematosus (SLE); (ii) 100 patients with SLE without SS; and (iii) 100 healthy blood donors from the blood bank of our hospital.
Only 11 (14%) patients with primary SS were found to have aPL (anticardiolipin antibodies or lupus anticoagulant, or both) in their sera, but anti beta 2-glycoprotein I antibodies were not detected in any patient. In contrast, aPL were detected in 12 (24%) patients with SS secondary to SLE and in 21 (21%) patients with SLE without SS. None of the healthy controls presented aPL in their sera. Patients with primary SS presented a lower prevalence of thrombocytopenia (p < 0.05) and livedo reticularis (p < 0.01) compared with the other two groups of patients. No patient with primary SS was diagnosed as having an antiphospholipid syndrome (APS), while 4 (8%) patients with secondary SS and 9 (9%) with SLE without SS were found to have APS (p < 0.05).
In patients with primary SS, aPL are present in a lower percentage than in patients with SS secondary to SLE or in patients with SLE without SS. The presence of aPL in these primary SS patients is not associated with the clinical events of APS.