Granular white blood cells (WBC) containing cytoplasmic inclusions are frequently present in the synovial fluid of patients with rheumatoid arthritis. These "inclusion body cells" or "ragocytes" may occasionally be found in joint effusions associated with other forms of arthritis, and Hollander et al1 reserve the specific term "RA cells" for inclusion body cells which release rheumatoid factor on disintegration. The finding of RA cells in pleural fluid as reported by Carmichael and Golding 2 appears to offer a useful diagnostic method in the investigation of pleural effusion of uncertain cause, and is of further interest since the existence of specific rheumatoid pleuritis is still questionable 3 although generally accepted.4
We have recently observed a patient with rheumatoid arthritis and pleural effusion in whom pleural RA cells with specific γ-globulin-containing phagosomes were demonstrated by immunofluorescent studies. The presence of specific rheumatoid involvement of the pleura was confirmed at autopsy.
Mandl MAJ, Watson JI, Henderson JAM, Wang N. Pleural Fluid in Rheumatoid PleuritisPatient Summary With Histopathologic Studies. Arch Intern Med. 1969;124(3):373–376. doi:10.1001/archinte.1969.00300190113019