The effectiveness of tocilizumab in treating refractory adult-onset Still's disease with dichotomous phenotypes: IL-18 is a potential predictor of therapeutic response.

AOSD patients refractory to high-dose corticosteroids and methotrexate may respond well to TCZ treatment with a steroid-sparing effect and an acceptable safety. A high baseline IL-18 level may be a predictor of poor therapeutic response. Key Points • Tocilizumab may be effective and well-tolerated in refractory AOSD patients regardless of disease subtypes. • High plasma levels of IL-18 may predict poor response to tocilizumab in AOSD patients.