Sulphasalazine-induced lupus in psoriatic arthritis.

Lupus syndromes have been described in rheumatoid arthritis and inflammatory bowel diseases treated with sulphasalazine. We describe two cases of lupus with clinical and serological disease, developing in seronegative, immunologically nude psoriatic arthritis following sulphasalazine treatment. On cessation of sulphasalazine the clinical and serologic features of lupus disappeared. This suggests that the lupus syndrome was induced by sulphasalazine rather than unmasked by it.