Table 1. Diagnostic criteria for hemophagocytic syndrome used in the HLH-2004 trial*.

The diagnosis of hemophagocytic syndrome may be established when:
A. Molecular diagnosis consistent with HLH: pathologic mutations of PRF1, UNC13D, Munc18-2, Rab27a, STX11, SH2D1A, or BIRC4
Or
B. Five of the 8 criteria listed below are fulfilled:
1. Fever ≥ 38.5 °C
2. Splenomegaly
3. Cytopenias (affecting at least 2 of 3 lineages in the peripheral blood):    Hemoglobin < 9 g/dL    Platelets < 100 × 103/mL    Neutrophils < 1 × 103/mL
4. Hypertriglyceridemia (fasting > 265 mg/dL) and/or hypofibrinogenemia (< 150 mg/dL)
5. Hemophagocytosis in bone marrow, spleen, lymph nodes, or liver
6. Low or absent NK-cell activity
7. Ferritin > 500 ng/mL
8. Elevated sCD25 (α-chain of sIL-2 receptor)

*Adopted from reference [8].