• juvenile idiopathic arthritis
• fever syndromes
• adult onset still's disease

We are grateful to Wang et al 1 for testing our diagnostic score for macrophage activation syndrome (MAS)2 in their patients with adult onset Still disease (AOSD). Because it is increasingly recognised that systemic juvenile idiopathic arthritis (sJIA) and AOSD represent the same disease occurring at different ages3 4 and considering that the two illnesses share a similar risk for MAS, it is important to investigate whether the current diagnostic tools are applicable to both conditions.

Wang and colleagues evaluated retrospectively the capacity of the MAS/sJIA (MS) score to detect MAS in AOSD by comparing 60 patients with MAS, whose diagnosis was made by HLH-2004 criteria and confirmed by the caring rheumatologists, with 390 patients without MAS. They found that the application of the MS score with the cut-off of ≥ –2.1 obtained in our study yielded a maximum …