An 84-year-old woman visited our hospital for dyspnea due to right pleural effusion, with lymphocytic dominance and a high adenosine deaminase (ADA) level, that had been noted 1 month earlier. She was suspected of having tuberculosis pleurisy; however, anti-tuberculosis treatment yielded no improvements. She was diagnosed with pleural effusion due to primary Sjögren's syndrome (SjS) based on her dry eyes and mouth, positivity for anti-Sjögren's-syndrome-related antigen A/B, and histopathologic findings of a lip biopsy and thoracoscopic pleural biopsy. Her symptoms improved after starting steroid therapy. Cases of pleural effusion due to SjS with a high ADA level may be misdiagnosed as tuberculosis pleurisy.
Keywords: Sjögren's syndrome; adenosine deaminase; pleural effusion; tuberculous pleurisy.