The diagnosis of HLH is based on clinical criteria. The most recent diagnostic guidelines were revised in 2004 [4] . HLH is diagnosed if either a molecular diagnosis consistent with HLH is made, or five of the eight following diagnostic criteria are met: 1.) fever; 2.) splenomegaly; 3.) cytopenias affecting at least two of three lineages in the peripheral blood (haemoglobin <90 g/L, platelets <100 × 10 9 /L, or neutrophils <1 × 10 9 /L); 4.) hypertriglyceridemia (fasting triglycerides ≥ 3 mmol/L (≥ 265 mg/ dL)) and/or hypofibrinogenemia (fibrinogen ≤ 1.5 mg/dL); 5.) hemophagocytosis in bone marrow, spleen, or lymph nodes (excluding signs of malignancy); 6.) low or absent NK-cell activity; 7.) hyperferritinemia (ferritin >500 μg/L); and 8.) high levels of sIL-2R (sIL-2R ≥ 2400 U/ml).