New Perspective on the Clinical and Laboratory Characteristics of Rheumatoid Pleural Effusion: A 29-Case Series.

Objective Rheumatoid pleural effusion (RPE) usually occurs in middle-aged men. Pleural fluid analyses have revealed high lactate dehydrogenase (LDH) levels and low pH and glucose levels in RPE. We aimed to investigate the clinical and laboratory features of patients with RPE since the beginning of the 21st century. Methods Medical records of patients with RPE were reviewed between May 2006 and October 2021. The patients were divided into <60-year (younger) and ≥60-year (older) groups. Results The younger group comprised 6 patients (median age 53.5 years, female 33%) and older group comprised 23 patients (median age 76 years, female 52.2%). Compared to the younger group, the older group had fewer cases of fever (83.3% vs. 18.2%, p = 0.007) and chest pain (66.7% vs. 8.7%, p = 0.008). In pleural fluid analysis, the older group presented higher pH (p = 0.004) and lower LDH levels (p = 0.044). Seven patients died during the follow-up period. Conclusion Most patients with RPE were over 60 years of age, and approximately half of them were female. The pleural fluid analysis showed milder inflammation in older patients than in middle-aged patients. The mortality rate of patients with RPE was distinctly higher than that previously reported.