After 49 days in hospital, hemophagocytic syndrome was diagnosed [persistent fever (> 38·5 °C); severe pancytopenia; hypertriglyceridemia; low and absent NK cell; ferritin concentrations on the 34th day:16,279.0 ng mL−1, IL-2R concentrations on the 34th day: 6757.0 IU ml−1; abdominal CT on the 41th day showed splenomegaly; bone marrow biopsy on the 42th day showed hemophagocytosis (Fig. 3)] [6, 7]. The gene discussed is IL2RA; the disease is hemophagocytic syndrome.