Synovial fluid characteristics and the lupus erythematosus cell phenomenon in drug-induced lupus. Findings in three patients and review of pertinent literature.

The characteristics of synovial fluid obtained from 3 patients with drug-induced lupus erythematosus are described. Two patients had "inflammatory" counts of synovial leukocytes, in the range of 2,500-39,000/mm3, with mononuclear predominance in 1 patient and neutrophil predominance in the other. The third patient had "noninflammatory" fluid, with mononuclear predominance. Lupus erythematosus cells formed in vivo were observed in the synovial fluid of 2 of the patients. Biopsy of the synovium of 1 patient showed nonspecific chronic inflammatory changes. Our findings in these patients with drug-induced lupus are indistinguishable from those previously described in patients with idiopathic lupus erythematosus.