IL2RA and Hypofibrinogenemia: In light of our findings (EBV infection, fever, splenomegaly, bicytopenia, hypertriglyceridemia, hypofibrinogenemia, hemophagocytosis, ferritin ≥ 500 μg/L, low NK-cell activity, and soluble CD25 ≥ 2,400 U/m), we consulted with an expert in infectious diseases and an expert in blood diseases to diagnose a chronic active EB virus infection (CAEBV) complicated with hemophagocytic lymphohistiocytosis (HLH), on the basis of the diagnostic criteria on the guideline for diagnosis and treatment of CAEBV in children and the HLH 2004 clinical trial (11–13).