In 157 women and 77 men with rheumatoid arthritis, observed for a mean of 5.7 years, the annual incidence of pleural effusion was found to be 0.34% in the women and 1.54% in the men. In 4 pleural fluids the fluid-to-serum ratio for Waaler-Rose titres was 1:4, which agrees with the ratios for other proteins and does not suggest a pathogenetic role of the rheumatoid factor. In two other pleural fluids the findings suggested immune mechanisms implicating the rheumatoid factor. In general, the data, both clinical and any other, was compatible with the possibility of multiple etiological and pathogenetic factors in rheumatoid pleural effusions. These were: extrinsic factors causing pleural thickenings in 25% of non-rheumatoid men and in less than 10% of non-rheumatoid women aged more than 50 years; preceding lung disorder; particular inflammatory responsiveness due to rheumatoid disease, related or unrelated to rheumatoid factor; and some degree of transudation.
The chest radiographs of 309 patients with rheumatoid arthritis (RA) were compared with those of 309 controls. In RA, lung nodules were present in 0.3% and pleural effusion in 0.6% only. Diffuse reticulonodular fibrosis occurred in 4.5% of the RA patients and 0.3% of the controls (p less than 0.001) and was related to subcutaneous nodules, antinuclear antibodies and high Waaler-Rose titres. Diffuse reticular fibrosis occurred in 6.8% and 5.2% respectively and was related only to age greater than 60 and cigarette smoking. Healed tuberculosis occurred in 17.2% of the RA males and in 6.1% of the male controls (p less than 0.025). Sequelae of pleurisy occurred in 16.2% of the RA females and in 8.1% of female controls (p less than 0.025) and was related to involvement of many joints and high ESR. Sequelae of pleurisy occurred in 24.2% of the RA males and 16.2% of the male controls. The pleuropulmonary findings were not related to the therapy given or to the death rate during a mean follow-up period of 5.7 years.