CD40LG and isolated hyperferritinemia: After being admitted, he received a red blood cell transfusion and was evaluated for pyrexia. Additional blood tests at our hospital revealed mild leukopenia (WBC: 3,870 /μL) and platelets (PLT: 24.7 × 104/μL), with hyperferritinemia (5,129 ng/mL), elevated soluble IL-2 receptor levels (1,179 U/mL), a mild decrease in fibrinogen (227 mg/dL), and positivity for PVB19 IgM (12.7 by enzyme immunoassay).