Prevalence of the antiphospholipid syndrome in primary systemic vasculitis.

Background: The antiphospholipid (APS or Hughes’) syndrome, anticardiolipin antibodies (aCL), and the lupus anticoagulant (LA) are associated with systemic lupus erythematosus, malignancy, infection, and drugs. It has been described in patients with primary systemic vasculitis (PSV). Objective: To determine the prevalence of APS in patients with PSV attending a vasculitis clinic and the prevalence of patients with positive aCL and/or the LA who do not fulfil the classification criteria for APS. Methods: All case notes of patients attending the vasculitis clinic over a 12 month period were reviewed. Outpatients and inpatients were both included and were assessed for features of the APS and presence of aPL. Patients with positive aCL or LA tests were classified according to the significance of these results. Results: Of 144 patients with PSV, 25 had positive aCL or LA on at least one occasion, representing a point prevalence of 17%. Of these, nine had definite APS (classified by the Sapporo criteria) and a further four patients had clinical and serological features of APS, although insufficient to satisfy the Sapporo criteria. Twelve had only positive aPL. Conclusion: The antiphospholipid syndrome, aCL, and the LA may occur in association with PSV.