IFNG and isolated hyperferritinemia: In this patient, the constellation of laboratory findings—including extreme hyperferritinemia, elevated inflammatory cytokines (IL-6, IL-10, TNF-α, IFN-γ), and multi-organ involvement—supports the presence of a cytokine storm or secondary HLH phenotype triggered by influenza A infection (Fiore-Gartland et al., 2017).