IL2RA and Hemophagocytosis: These include: 1) fever >38.5oC, 2) splenomegaly, 3) cytopenias affecting at least two of three lineages [hemoglobin ≤ 9 g/dL, platelets < 100,000/mm3, neutrophils < 1 × 103/mm3], 4) hypertriglyceridemia (>=265 mg/dL) and/or hypofibrinogenemia (<=250 mg/dL), 5) hemophagocytosis in bone marrow, spleen, or lymph nodes, 6) low or absent NK cell activity, 7) high ferritin level (>=500 μg/L), and 8) elevated soluble CD25 (IL-2 receptor α >= 2,400 U/mL) [7].