Systemic juvenile idiopathic arthritis (sJIA) is a distinct clinical spectrum of illnesses compared to other types of chronic arthritides in children. Typically, the clinical features include the characteristic quotidian fevers, evanescent rashes, serositis, lymphadenopathy and hepatosplenomegaly in addition to persistent and destructive arthritis at the severe end of the spectrum. The children also appear to be more prone to macrophage activation syndrome/secondary histiolymphocytic haemophagocytosis (HLH). It is generally acknowledged that a similar disease occurs rarely in adults: adult onset Still disease (AOSD). However, the clinical classifications for each were developed separately and are different from each other. The Yamaguchi AOSD criteria1 are less precise in the exclusions and are able to include a wider spectrum of clinical manifestations as compared to the International League of Associations for Rheumatology (ILAR) classification of sJIA.2

The pathogenesis of sJIA is still the subject of much research and the first reports of the role of interleukin (IL)-1 in sJIA by Verbsky et al,3 and Pascual et al4 have raised the hope that both the pathogenesis and treatment of this disease are finally being elucidated. Similarly in AOSD, Fujii et al5 and Fitzgerald et al6 found success in treating AOSD with anakinra, a recombinant form of the IL-1 receptor antagonist. The paper by Lequerre et al7 in this …