Abstract: We report a case of fever, myalgia and pleural effusion in which inflammatory markers were significantly elevated during the course of the disease. Pleural effusion was exudate and white blood cell count was significantly elevated, It is dominated by neutrophile granulocyte. After the infection was fully ruled out, the final diagnosis was adult-onset Still's disease. The clinical symptoms were relieved after treatment with glucocorticoid and tocilizumab.