Differentially expressed probe sets and hierarchic clustering in patients with sJIA and anemia compared with patients with non-sJIA and anemia and hierarchic clustering of controls, patients with sJIA, and those with FHLH. (a) Gene expression of 671 probes that are differentially expressed between 18 patients with systemic arthritis and anemia and 22 patients with other subtypes of JIA and anemia. Genes and samples are clustered by using hierarchic clustering. Four clusters are designated with Roman numerals. (b) Gene-expression pattern of 67 probes ("erythropoiesis signature") among healthy controls, patients with familial HLH, systemic arthritis without MAS, and systemic arthritis with MAS. Samples are clustered by using euclidean distances.