IgE rheumatoid factor in a case of rheumatoid arthritis with pleuritis.

IgE rheumatoid factor (RF) was detected in sera from 4 out of approximately 100 rheumatoid patients using a solid phase enzyme-linked immunosorbent assay. All 4 patients had extraarticular lesions. A quantitative analysis revealed that over 60% of total IgE in the serum and pleural fluid from a rheumatoid patient with pleuritis had RF activity. The changes in the level of serum IgE RF in our case paralleled the disease activity. This study suggests that IgE RF may play some role in the pathogenesis of certain extraarticular features of RA.