Abstract
We report a 64-year-old female case of intractable adult-onset Still's disease (AOSD). Initial high-dose steroid therapy combined with cyclosporin A was ineffective against macrophage-activation syndrome (MAS), which was accompanied by the systemic type of AOSD. Treatment for MAS with intravenous cyclophosphamide resulted in remission of AOSD and a reduction in the high doses of steroids. Efficacy of biologics against MAS in AOSD is unclear. Cyclophosphamide, a conventional cytotoxic agent, should be considered as one of the therapeutic options for refractory types of AOSD with MAS.