Sulphasalazine-induced autoimmune abnormalities in patients with rheumatic disease.

Sulphasalazine is a commonly used second line agent in rheumatoid arthritis (RA) and other inflammatory joint diseases and is reported to be one of the least toxic of this group of drugs. Recently a severe allergic reaction and cases of lupus-like disease have been described in patients with RA after treatment with sulphasalazine. We describe five patients, all with inflammatory arthropathy who developed cutaneous vasculitis, lupus-like disease or atypical serology after exposure to sulphasalazine. Three of four cases investigated were found to have the slow acetylator phenotype. These reactions can complicate the diagnosis and delay discontinuation of the drug. Moreover, present guidelines for the diagnosis of drug-induced lupus do not apply to the majority of patients with sulphasalazine-induced lupus.