However high levels for IL-1RA (reference range 78-970 pg/ml) were detected in both groups: sJIA (Me 1267,43 pg/ml [interquartile range (IQR) 936,75; 2292,75]) and FOP (Me 1342,36 pg/ml [IQR 927,0; 1811,6]) and values of FOP pts were higher than in 44 sJIA pts without macrophage activation syndrome (MAS) (Me 1165,2 pg/ml [IQR 868,0; 1743,8]) and lower than in 8 sJIA pts with MAS (Me 2654,2 pg/ml [IQR 1432,2; 6252,2]). Here, IL6R is linked to macrophage activation syndrome.