Except for SJIA and KD, serum cytokines were not checked in most patients with other differential diseases, such as infectious lymphadenitis, lymphoma, etc. Future prospective studies with large sample sizes and more control groups may further explore the exact role of serum IFN-γ, IL-6, and IFN-γ/IL-6 ratio in the KFD diagnosis. This evidence concerns the gene IFNG and systemic-onset juvenile idiopathic arthritis.