Rheumatoid pleural effusion presenting as pseudochylothorax in a patient without previous diagnosis of rheumatoid arthritis

BACKGROUND: Rheumatoid pleurisy rarely occurs before a diagnosis of rheumatoid arthritis (RA). It is the second leading cause of pseudochylothorax, but there are few reports of RA-associated pseudochylothorax. CASE: A 50-year-old man presented to our hospital with an undiagnosed exudative pleural effusion. In order to obtain a definitive diagnosis, we performed medical thoracoscopy under local anesthesia. The pleural effusion was turbid and was identified as a pseudochylothorax. The parietal pleura was white and slightly thickened with numerous scattered small granules and the pleural biopsy showed an infiltration of inflammatory cells including lymphocytes and plasma cells with a lack of normal mesothelial cells, findings that were highly consistent with rheumatoid pleurisy. Additional laboratory data revealed elevated levels of CCP antibody and rheumatoid factor. During an outpatient visit about 30 days after discharge, the patient complained of polyarthralgia and was diagnosed with RA, resulting in a definitive diagnosis of the pleural effusion as rheumatoid pleurisy. CONCLUSION: We encountered a rare case of a rheumatoid pleural effusion without other symptoms of arthritis, which was identified as a pseudochylothorax by medical thoracoscopy.