Clinical utility and serological connections of anti-RA33 antibodies in systemic lupus erythematosus.

To determine whether the autoantibody anti-RA33, first identified in patients with rheumatoid arthritis, could define a subset of patients with lupus. Sera from 30 patients with systemic lupus erythematosus (SLE), including serial bleeds from 8 patients were tested for anti-RA33 antibodies by immunoblotting. The results were compared to a wide range of SLE clinical features using the British Isles Lupus Assessment Group system and serological abnormalities. 12 of the 30 patients had RA33 antibodies. Their presence was associated with erosive arthropathy, and a lack of dermatological involvement in patients less likely to be Caucasian. The presence of anti-RA33 antibodies appears to identify a subset of patients with SLE.