Exacerbation of adult-onset Still's disease, possibly related to elevation of serum tumor necrosis factor-alpha after etanercept administration.

Adult-onset Still's disease (AOSD) is a systemic inflammatory disease of unknown etiology. A 44-year-old male patient presented with AOSD complicated by macrophage activation syndrome after etanercept therapy. His serum tumor necrosis factor-α (TNF-α) level was increased dramatically after etanercept therapy. The clinical course of this case suggests that the increased TNF-α level by etanercept administration might cause macrophage activation syndrome in this case.