High pleural fluid hyaluronan concentrations in rheumatoid arthritis

Previous studies have shown that high pleural fluid (Pf) hyaluronan (HYA) c oncentrations may be due not only to malignant mesothelioma but also to inf lammatory diseases. The objective of this study was to evaluate Pf-HYA in v arious nonmalignant inflammatory pleural disorders. A radiometric assay was used to determine HYA in Pf acid serum (S) of 126 p atients, 12 of whom had rheumatoid arthritis (RA), 22 tuberculosis, 22 pneu monia, 41 lung cancer, 10 malignant mesothelioma and 19 congestive heart fa ilure. Pf-HYA values were correlated with values for Pf-tumour necrosis fac tor (TNF)-alpha and Pf-interleukin (IL)-1 beta, as determined by radioimmun oassay. The highest median Pf-HYA (125.6 mg.L-1, range 0.04-386.5 mg.L-1) occurred in patients with malignant mesothelioma. Among patients with nonmalignant i nflammatory diseases, significantly higher median Pf-HYA were observed in t hose with rheumatoid arthritis (64.2 mg.L-1, range 25.8-106.9 mg.L-1) than in those,vith tuberculosis (25.5 mg.L-1, range 14.9-57.1 mg.L-1, p<0.0005) or pneumonia (20.9 mg.L-1, range 9.5-129.4 mg.L-1, p<0.005). There was no c orrelation between Pf-HYA and S-HYA. Pf-HYA correlated positively with Pf-T NF-alpha (r=0.62) and Pf-IL-1 beta (r=0.52). High pleural fluid hyaluronan occurs not only in malignant mesothelioma, bu t also in certain nonmalignant inflammatory diseases, especially rheumatoid arthritis. One explanation for the increase in pleural fluid hyaluronan ma y be local production of proinflammatory cytokines, such as tumour necrosis factor-alpha and interleukin-1 beta.