Initial laboratory studies in the PICU revealed excessive hyperferritinemia (58360 ng/mL, reference range: 11.0-306.8 ng/mL), low natural killer (NK) cell activity (0.32 %, reference range: 5-26%), hypofibrinogenemia (0.84 g/l, reference range: 1.50-4.35 g/l), leukopenia (2.07×109/L, reference range: 3.5-9.5×109/L), neutropenia (0.92×109/L, reference range: 1.8-6.3×109/L) elevated international normalized ratio (INR) values (1.92, reference range: 0.8-1.2) and thrombocytopenia (42×109/L, reference range: 125-350×109/L), elevated alanine transaminase (ALT) levels (921 U/L, reference range: 7-40 U/L), aspartate aminotransferase (AST) levels (2223 U/L, reference range: 13-35 U/L), and total bilirubin (TBIL) levels (108.7 umol/L, reference range: 3.5-23.5 umol/L). The patient exhibited high levels of C reactive protein (CRP) (76.40 mg/L, reference range: 0-8 mg/L), procalcitonin (PCT) (2.73 ng/ml, reference range: 0-0.05 ng/ml), IL-6 (154.06 pg/ml, reference range: 0-5.4 pg/ml), IL-8 (32.67 pg/ml, reference range: 0-20.6 pg/ml), IL-10 (169.81 pg/ml, reference range: 0-12.9 pg/ml), and IFN-γ (4387.41 pg/ml, reference range: 0-23.1 pg/ml). EBV-DNA loads were significantly elevated (3.82×106 copies/ml). Multiple blood and sputum cultures as well as the other viral polymerase chain reaction (PCR) tests for common respiratory viruses and cytomegalovirus (CMV) were all negative. The bone marrow biopsy revealed the presence of hemophagocytosis.