A case of synovitis-acne-pustulosis-hyperostosis-osteitis syndrome with right pleural effusion.

A 79-year-old man presented with fatigue and right shoulder pain. Computed tomography revealed right pleural effusion and osteosclerosis of the sternoclavicular joint. There were no signs of malignancy or infection in the pleural fluid studies. His bone scintigraphy exhibited the "bull's head sign." Despite the absence of skin lesions, he was diagnosed with synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome. Remission was achieved after treatment with non-steroidal anti-inflammatory drugs and oral prednisolone. SAPHO syndrome causes pleural effusion, even in patients without skin lesions. Bone scintigraphy should be considered in the workup for patients with unexplained pleural effusion.