Rheumatoid pleural effusion presenting as pseudochylothorax in a patient without previous diagnosis of rheumatoid arthritis
A 50-year-old man, a truck driver and current smoker, was first found to have an asymptomatic right pleural effusion on chest radiography at a medical examination in September 2011. There had been no abnormal signs at the previous year's exam. His past medical history and family history were non-contributory.\nTwo rounds of thoracocentesis were performed without definitive diagnosis (September and November 2011). The patient remained asymptomatic and was followed with no treatment, but the pleural effusion gradually increased and he was referred to our hospital in October 2012. The chest radiograph on admission confirmed a moderate right-sided pleural effusion (). Blood tests revealed slight abnormalities of C-reactive protein (CRP) level (0.4 mg/dl), erythrocyte sedimentation rate (ESR) (39 mm/h), and triglyceride and total cholesterol levels (244 mg/dl, 238 mg/dl, respectively). There was a slight pleural thickening on the CT scan with pleural phase contrast enhancement, but there was no evidence of pulmonary tuberculosis, interstitial pneumonia, or other disease in the lung field ().\nWe performed medical thoracoscopy under local anesthesia for definitive diagnosis. The pleural fluid was turbid and the pleura was slightly thickened with a scattered granular appearance. A soft yellow material was found on the visceral and parietal pleura and fibrin deposition was recognized in the thoracic cavity ().\nThe pleural fluid was confirmed as pseudochylothorax because it had high cholesterol and low triglyceride concentrations (248 mg/dL and 12 mg/dL, respectively). And low glucose (6.0 mg/dl), high lactate dehydrogenase (LDH) (2438U/l), a slight elevation in adenosine deaminase (ADA) (57.7 μg/ml), and low complement C3 and C4 levels (13 mg/dl, 2.9 mg/dl, respectively) were noted. No malignant cells were found in the cytologic examination of the pleural fluid. There were sparse macrophages and neutrophils dispersed in the granular materials and no mesothelial cells were found. Microbiologic smears and cultures of pleural fluid showed no growth. Biopsy of the parietal pleura showed infiltration with inflammatory cells including lymphocytes and plasma cells and a lack of normal mesothelial cells, which was highly suspicious for rheumatoid pleurisy, although an obvious rheumatoid nodule was not observed.\nThe slight elevation in the ADA level of the pleural fluid may have also been consistent with tuberculous pleurisy, but this was ruled out by culture and biopsy findings. Additional laboratory data showed elevated levels of rheumatoid factor (RF) (72 units/mL, normal <15) and anti-cyclic citrullinated peptide (anti-CCP) antibody (6.8 units/mL, normal <4.4).\nThe discharge diagnosis of highly suspected rheumatoid pleurisy was based on the clinical features and the results of the above-stated studies, although the high pH and absence of RF in the pleural effusion were atypical. The patient's right lung was well expanded and decortication was not necessary.\nAt about 30 days after discharge, the patient presented with polyarthralgia and we were able to confirm the diagnosis of RA according to the 2010 RA classification criteria .