This premise is important to picture the multiple biological and pathophysiologic roles of IL-6 and to explain why IL-6 is a key factor in such a different disease as rheumatoid arthritis (RA) [51,52], juvenile idiopathic arthritis (JIA) [53], adult-onset Still’s disease (AOSD) [54], giant cell arteritis (GCA) [55] and Castleman disease [56], cytokine release syndrome, and uveitis [19]. This evidence concerns the gene IL6 and Castleman disease.