CHI3L1 and rheumatoid arthritis: Chitinase-3-like protein 1 (CHI3L1), a highly evolutionarily conserved secreted protein, have an important role in the pathogenesis of inflammatory diseases because of its upregulation in inflamed tissues of ulcerative colitis, Crohn’s disease, rheumatoid arthritis, osteoarthritis and liver cirrhosis, as well as in solid cancers6–9.