Interleukin-18 (IL-18) levels are strongly associated with AOSD.[4–9] In fact, IL-18 measurement is useful for differentiating AOSD from other diseases, particularly infections, and collagen disorders, as well as in determining disease severity and treatment response.[4–8] Although some case reports suggest that IL-18 measurement is useful for assessing AOSD severity,[9] there are few reports on the use of repeated IL-18 measurements throughout the full management course of AOSD as a guide for differential diagnosis and treatment. Here, IL18 is linked to adult-onset Still disease.