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Rheumatoid Pleural Effusion — SCE Rheumatology MCQ

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HardRheumatoid ArthritisRheumatoid Pleural EffusionSCE Rheumatology

A 60-year-old woman with long-standing seropositive erosive rheumatoid arthritis and rheumatoid nodules develops progressive dyspnoea over 6 weeks. She is afebrile and has no cough. CT pulmonary angiography shows bilateral pleural effusions with mild smooth pleural thickening, but no pulmonary embolus, focal consolidation or pleural or lung mass. Pleural fluid is an exudate: glucose 0.8 mmol/L, pH 7.15, protein 48 g/L and LDH 1,850 IU/L. Gram stain and bacterial and mycobacterial cultures are negative. Cytology from two samples shows no malignant cells. What is the most likely cause of the effusions?

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Correct answer: A — Rheumatoid pleural effusion

The correct answer is A, rheumatoid pleural effusion. Rheumatoid pleuritis classically produces an exudate with strikingly low glucose, acidic pH and high LDH, particularly in patients with seropositive, nodular RA. A complicated parapneumonic effusion is the most important mimic because it may also have pH below 7.20, low glucose and high LDH; however, the absence of fever, cough or consolidation and the negative cultures argue against infection. Malignant effusions can occasionally have low glucose and pH, and negative cytology alone is not conclusive, but repeated negative cytology and the absence of a mass make malignancy less likely. Pulmonary embolism is excluded by CT angiography. Heart-failure effusions are usually transudative and do not ordinarily produce this profoundly low glucose and pH.

Reference: Minoda SS et al. New perspective on the clinical and laboratory characteristics of rheumatoid pleural effusion: A 29-case series. Modern Rheumatology. 2025;35(2):249-255. https://pubmed.ncbi.nlm.nih.gov/39172636/