In rheumatoid arthritis, FGF23 enhanced a proinflammatory cytokine, IL-1β, in synovial fibroblasts through FGF23-FGFR1c-mediated PI3K-Akt and NF-κB pathways promoting joint pain, swelling, and bone deformities [301]. The gene discussed is FGF23; the disease is rheumatoid arthritis.