HLH2004 standard at least 5 criteria out of the following: Fever ≥ 38.5 ℃ for ≥ 7 days; hepatosplenomegaly; Cytopenias affecting ≥ 2 of 3 lineages in PB Hb < 9 g/L Platelet < 100 x 109 /L ANC < 1.0 x 109 /L; Hypertriglyceridemia and/or hypofibrinogenemia (fasting triglycerides ≥ 265 mg/dL, fibrinogen ≤ 1.5 g/L); Hemophagocytosis in BM or spleen or LN; Low or absent NK-cell activity ( according to local laboratory reference); Serum-ferritin ≥ 500 mcg/L ; Soluble CD25(sIL-2 receptor) ≥ 2,400 U/ml ;